id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1804.03297 | P Ajith | Siddharth Dhanpal, Abhirup Ghosh, Ajit Kumar Mehta, Parameswaran
Ajith, B. S. Sathyaprakash | A "no-hair" test for binary black holes | 5 pages, 4 figures | Phys. Rev. D 99, 104056 (2019) | 10.1103/PhysRevD.99.104056 | LIGO-P1800056-v4 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the consequences of the black-hole "no-hair" theorem in general
relativity (GR) is that gravitational radiation (quasi-normal modes) from a
perturbed Kerr black hole is uniquely determined by its mass and spin. Thus,
the spectrum of quasi-normal mode frequencies have to be all consistent with
the same value of the mass and spin. Similarly, the gravitational radiation
from a coalescing binary black hole system is uniquely determined by a small
number of parameters (masses and spins of the black holes and orbital
parameters). Thus, consistency between different spherical harmonic modes of
the radiation is a powerful test that the observed system is a binary black
hole predicted by GR. We formulate such a test, develop a Bayesian
implementation, demonstrate its performance on simulated data and investigate
the possibility of performing such a test using previous and upcoming
gravitational wave observations.
| [
{
"created": "Tue, 10 Apr 2018 01:22:10 GMT",
"version": "v1"
}
] | 2019-05-29 | [
[
"Dhanpal",
"Siddharth",
""
],
[
"Ghosh",
"Abhirup",
""
],
[
"Mehta",
"Ajit Kumar",
""
],
[
"Ajith",
"Parameswaran",
""
],
[
"Sathyaprakash",
"B. S.",
""
]
] | One of the consequences of the black-hole "no-hair" theorem in general relativity (GR) is that gravitational radiation (quasi-normal modes) from a perturbed Kerr black hole is uniquely determined by its mass and spin. Thus, the spectrum of quasi-normal mode frequencies have to be all consistent with the same value of the mass and spin. Similarly, the gravitational radiation from a coalescing binary black hole system is uniquely determined by a small number of parameters (masses and spins of the black holes and orbital parameters). Thus, consistency between different spherical harmonic modes of the radiation is a powerful test that the observed system is a binary black hole predicted by GR. We formulate such a test, develop a Bayesian implementation, demonstrate its performance on simulated data and investigate the possibility of performing such a test using previous and upcoming gravitational wave observations. |
1312.6810 | Brian Dolan | Brian P. Dolan | On the thermodynamic stability of rotating black holes in higher
dimensions -- a comparison of thermodynamic ensembles | 41 pages, 5 figures; typo in appendix D corrected in v4 | null | 10.1088/0264-9381/31/13/135012 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Thermodynamic potentials relevant to the micro-canonical, the canonical and
the grand-canonical ensembles, associated with rotating black holes in
D-dimensions, are analysed and compared. Such black holes are known to be
thermodynamically unstable, but the instability is a consequence of a subtle
interplay between specific heats and the moments of inertia and it manifests
itself differently in the different ensembles. A simple relation between the
product of the specific heat and the determinant of the moment of inertia in
both the canonical and the grand-canonical ensembles is derived. Myers-Perry
black holes in arbitrary dimension are studied in detail. All temperature
extrema in the micro-canonical ensemble are determined and classified. The
specific heat and the moment of inertia tensor are evaluated in both the
canonical and the grand-canonical ensembles in any dimension. All zeros and
poles of the specific heats, as a function of the angular momenta, are
determined and the eigenvalues of the isentropic moment of inertia tensor are
also found and classified. It is further shown that many of the thermodynamic
properties of a Myers-Perry black hole in D-2 dimensions can be obtained from
those of a black hole in D dimensions by sending one of the angular momenta to
infinity.
| [
{
"created": "Tue, 24 Dec 2013 12:54:21 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Jan 2014 17:01:18 GMT",
"version": "v2"
},
{
"created": "Thu, 8 May 2014 15:20:43 GMT",
"version": "v3"
},
{
"created": "Mon, 16 Jun 2014 15:14:12 GMT",
"version": "v4"
}
] | 2015-06-18 | [
[
"Dolan",
"Brian P.",
""
]
] | Thermodynamic potentials relevant to the micro-canonical, the canonical and the grand-canonical ensembles, associated with rotating black holes in D-dimensions, are analysed and compared. Such black holes are known to be thermodynamically unstable, but the instability is a consequence of a subtle interplay between specific heats and the moments of inertia and it manifests itself differently in the different ensembles. A simple relation between the product of the specific heat and the determinant of the moment of inertia in both the canonical and the grand-canonical ensembles is derived. Myers-Perry black holes in arbitrary dimension are studied in detail. All temperature extrema in the micro-canonical ensemble are determined and classified. The specific heat and the moment of inertia tensor are evaluated in both the canonical and the grand-canonical ensembles in any dimension. All zeros and poles of the specific heats, as a function of the angular momenta, are determined and the eigenvalues of the isentropic moment of inertia tensor are also found and classified. It is further shown that many of the thermodynamic properties of a Myers-Perry black hole in D-2 dimensions can be obtained from those of a black hole in D dimensions by sending one of the angular momenta to infinity. |
gr-qc/0605028 | M. Alessandra Papa | The LIGO Scientific Collaboration | Coherent searches for periodic gravitational waves from unknown isolated
sources and Scorpius X-1: results from the second LIGO science run | 35 pages, 30 figures | Phys.Rev.D76:082001,2007 | 10.1103/PhysRevD.76.082001 | LIGO-P050008-03 | gr-qc | null | We carry out two searches for periodic gravitational waves using the most
sensitive few hours of data from the second LIGO science run. The first search
is targeted at isolated, previously unknown neutron stars and covers the entire
sky in the frequency band 160-728.8 Hz. The second search targets the accreting
neutron star in the low-mass X-ray binary Scorpius X-1, covers the frequency
bands 464-484 Hz and 604-624 Hz, and two binary orbit parameters. Both searches
look for coincidences between the Livingston and Hanford 4-km interferometers.
For isolated neutron stars our 95% confidence upper limits on the
gravitational wave strain amplitude range from 6.6E-23 to 1E-21 across the
frequency band; For Scorpius X-1 they range from 1.7E-22 to 1.3E-21 across the
two 20-Hz frequency bands. The upper limits presented in this paper are the
first broad-band wide parameter space upper limits on periodic gravitational
waves using coherent search techniques. The methods developed here lay the
foundations for upcoming hierarchical searches of more sensitive data which may
detect astrophysical signals.
| [
{
"created": "Thu, 4 May 2006 22:41:39 GMT",
"version": "v1"
},
{
"created": "Wed, 31 May 2006 22:37:31 GMT",
"version": "v2"
}
] | 2012-08-27 | [
[
"The LIGO Scientific Collaboration",
"",
""
]
] | We carry out two searches for periodic gravitational waves using the most sensitive few hours of data from the second LIGO science run. The first search is targeted at isolated, previously unknown neutron stars and covers the entire sky in the frequency band 160-728.8 Hz. The second search targets the accreting neutron star in the low-mass X-ray binary Scorpius X-1, covers the frequency bands 464-484 Hz and 604-624 Hz, and two binary orbit parameters. Both searches look for coincidences between the Livingston and Hanford 4-km interferometers. For isolated neutron stars our 95% confidence upper limits on the gravitational wave strain amplitude range from 6.6E-23 to 1E-21 across the frequency band; For Scorpius X-1 they range from 1.7E-22 to 1.3E-21 across the two 20-Hz frequency bands. The upper limits presented in this paper are the first broad-band wide parameter space upper limits on periodic gravitational waves using coherent search techniques. The methods developed here lay the foundations for upcoming hierarchical searches of more sensitive data which may detect astrophysical signals. |
2306.12455 | Faizuddin Ahmed | Faizuddin Ahmed | Gravitational lensing in a space-time with cosmic string within the
Eddington-inspired Born-Infeld gravity | 9 pages, 4 figures, accepted in IJGMMP
(https://doi.org/10.1142/S0219887824501871) | null | 10.1142/S0219887824501871 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | This study explores the deflection angle of photon rays or light-like
geodesics within the framework of Eddington-inspired Born-Infeld (EiBI) gravity
background space-time, taking into account the influence of cosmic strings. The
primary focus lies in deriving the effective potential of the system applicable
to both null and time-like geodesics, as well as determining the angle of
deflection for light-like geodesics. Our analysis shows that the presence of
cosmic strings induces modifications in these physical quantities, leading to
shifts in their respective values.
| [
{
"created": "Wed, 21 Jun 2023 05:22:32 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Jun 2023 08:27:24 GMT",
"version": "v2"
},
{
"created": "Fri, 29 Mar 2024 07:59:00 GMT",
"version": "v3"
}
] | 2024-04-01 | [
[
"Ahmed",
"Faizuddin",
""
]
] | This study explores the deflection angle of photon rays or light-like geodesics within the framework of Eddington-inspired Born-Infeld (EiBI) gravity background space-time, taking into account the influence of cosmic strings. The primary focus lies in deriving the effective potential of the system applicable to both null and time-like geodesics, as well as determining the angle of deflection for light-like geodesics. Our analysis shows that the presence of cosmic strings induces modifications in these physical quantities, leading to shifts in their respective values. |
1204.1684 | Atsushi Higuchi | Atsushi Higuchi | Equivalence between the Weyl-tensor and gauge-invariant graviton
two-point functions in Minkowski and de Sitter spaces | 6 pages, revised and extended version of a talk; minor errors
corrected; proof for de Sitter space improved | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The two-point Wightman function of the free photon field defined in a
gauge-invariant manner is known to be equivalent to the field-strength
two-point function in any spacetime that is topologically trivial. We show that
the gauge-invariant graviton two-point function defined in a similar manner is
equivalent to the Weyl-tensor two-point function in Minkowski space and in the
Poincare patch of de Sitter space. This implies that in the Poincare patch of
de Sitter space the gauge-invariant graviton two-point function decays like
(distance)^(-4) as a function of coordinate distance for spacelike separation.
| [
{
"created": "Sat, 7 Apr 2012 21:46:43 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Aug 2013 10:32:32 GMT",
"version": "v2"
},
{
"created": "Thu, 22 Aug 2013 14:20:39 GMT",
"version": "v3"
}
] | 2013-08-23 | [
[
"Higuchi",
"Atsushi",
""
]
] | The two-point Wightman function of the free photon field defined in a gauge-invariant manner is known to be equivalent to the field-strength two-point function in any spacetime that is topologically trivial. We show that the gauge-invariant graviton two-point function defined in a similar manner is equivalent to the Weyl-tensor two-point function in Minkowski space and in the Poincare patch of de Sitter space. This implies that in the Poincare patch of de Sitter space the gauge-invariant graviton two-point function decays like (distance)^(-4) as a function of coordinate distance for spacelike separation. |
gr-qc/9607069 | Chris Isham | C.J. Isham | Topos Theory and Consistent Histories: The Internal Logic of the Set of
all Consistent Sets | 28 pages, LaTeX | Int.J.Theor.Phys. 36 (1997) 785-814 | 10.1007/BF02435786 | Imperial/TP/95--96/55 | gr-qc quant-ph | null | A major problem in the consistent-histories approach to quantum theory is
contending with the potentially large number of consistent sets of history
propositions. One possibility is to find a scheme in which a unique set is
selected in some way. However, in this paper we consider the alternative
approach in which all consistent sets are kept, leading to a type of `many
world-views' picture of the quantum theory. It is shown that a natural way of
handling this situation is to employ the theory of varying sets (presheafs) on
the space $\B$ of all Boolean subalgebras of the orthoalgebra $\UP$ of history
propositions. This approach automatically includes the feature whereby
probabilistic predictions are meaningful only in the context of a consistent
set of history propositions. More strikingly, it leads to a picture in which
the `truth values', or `semantic values' of such contextual predictions are not
just two-valued (\ie true and false) but instead lie in a larger logical
algebra---a Heyting algebra---whose structure is determined by the space $\B$
of Boolean subalgebras of $\UP$.
| [
{
"created": "Sun, 28 Jul 1996 09:00:34 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Isham",
"C. J.",
""
]
] | A major problem in the consistent-histories approach to quantum theory is contending with the potentially large number of consistent sets of history propositions. One possibility is to find a scheme in which a unique set is selected in some way. However, in this paper we consider the alternative approach in which all consistent sets are kept, leading to a type of `many world-views' picture of the quantum theory. It is shown that a natural way of handling this situation is to employ the theory of varying sets (presheafs) on the space $\B$ of all Boolean subalgebras of the orthoalgebra $\UP$ of history propositions. This approach automatically includes the feature whereby probabilistic predictions are meaningful only in the context of a consistent set of history propositions. More strikingly, it leads to a picture in which the `truth values', or `semantic values' of such contextual predictions are not just two-valued (\ie true and false) but instead lie in a larger logical algebra---a Heyting algebra---whose structure is determined by the space $\B$ of Boolean subalgebras of $\UP$. |
1704.02461 | David McNutt | David D. McNutt, Don N. Page | Scalar Polynomial Curvature Invariant Vanishing on the Event Horizon of
Any Black Hole Metric Conformal to a Static Spherical Metric | 5 pages, minor corrections to two equations and references | Physical Review D, 95, 084044 (2017) | 10.1103/PhysRevD.95.084044 | Alberta-Thy 2-17 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a scalar polynomial curvature invariant that transforms
covariantly under a conformal transformation from any spherically symmetric
metric. This invariant has the additional property that it vanishes on the
event horizon of any black hole that is conformal to a static spherical metric.
| [
{
"created": "Sat, 8 Apr 2017 09:32:34 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Apr 2017 09:19:01 GMT",
"version": "v2"
}
] | 2017-04-26 | [
[
"McNutt",
"David D.",
""
],
[
"Page",
"Don N.",
""
]
] | We construct a scalar polynomial curvature invariant that transforms covariantly under a conformal transformation from any spherically symmetric metric. This invariant has the additional property that it vanishes on the event horizon of any black hole that is conformal to a static spherical metric. |
0906.0677 | Bin Wang | Jian-Hua He, Bin Wang, Pengjie Zhang | The imprint of the interaction between dark sectors in large scale
cosmic microwave background anisotropies | 17 pages, 9 figures, revised version, more discussions added,
accepted for publication in PRD | Phys.Rev.D80:063530,2009 | 10.1103/PhysRevD.80.063530 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dark energy interacting with dark matter is a promising model to solve the
cosmic coincidence problem. We study the signature of such interaction on large
scale cosmic microwave background (CMB) temperature anisotropies. Based on the
detail analysis in perturbation equations of dark energy and dark matter when
they are in interaction, we find that the large scale CMB, especially the late
Integrated Sachs Wolfe effect, is a useful tool to measure the coupling between
dark sectors. We also discuss the possibility to detect the coupling by
cross-correlating CMB maps with tracers of the large scale structure. We
finally perform the global fitting to constrain the coupling by using the CMB
power spectrum data together with other observational data. We find that in the
$1\sigma$ range, the constrained coupling between dark sectors can solve the
coincidence problem.
| [
{
"created": "Wed, 3 Jun 2009 10:00:45 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Aug 2009 14:45:53 GMT",
"version": "v2"
}
] | 2009-11-06 | [
[
"He",
"Jian-Hua",
""
],
[
"Wang",
"Bin",
""
],
[
"Zhang",
"Pengjie",
""
]
] | Dark energy interacting with dark matter is a promising model to solve the cosmic coincidence problem. We study the signature of such interaction on large scale cosmic microwave background (CMB) temperature anisotropies. Based on the detail analysis in perturbation equations of dark energy and dark matter when they are in interaction, we find that the large scale CMB, especially the late Integrated Sachs Wolfe effect, is a useful tool to measure the coupling between dark sectors. We also discuss the possibility to detect the coupling by cross-correlating CMB maps with tracers of the large scale structure. We finally perform the global fitting to constrain the coupling by using the CMB power spectrum data together with other observational data. We find that in the $1\sigma$ range, the constrained coupling between dark sectors can solve the coincidence problem. |
2305.07541 | Ayan Banerjee | Ayan Banerjee, Takol Tangphati and Anirudh Pradhan | Wormholes and energy conditions in $f(R,T)$ gravity | 8 pages, 3 figures, typo fixed; new references added | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the existence of wormholes in the context of $f(R,T)$ gravity. The
$f(R,T)$ theory is a curvature-matter coupled modified gravity that depends on
an arbitrary function of the Ricci scalar $R$ and the trace of the
stress-energy tensor $T$. In this work, we adopt two different choices for the
matter Lagrangian density ($\mathcal{L}_m= \mathcal{P}$ and $\mathcal{L}_m=
p_r$) and investigate the impact of each one on wormhole structure. By
adequately specifying the redshift function and the shape function, we found a
variety of exact wormhole solutions in the theory. Our finding indicates that,
for both classes of wormholes the energy density is always positive throughout
the spacetime, while the radial pressure is negative. This means exotic matter
is necessary for the existence of wormholes in $f(R,T)$ gravity.
| [
{
"created": "Fri, 12 May 2023 15:07:32 GMT",
"version": "v1"
},
{
"created": "Tue, 23 May 2023 07:36:04 GMT",
"version": "v2"
}
] | 2023-05-24 | [
[
"Banerjee",
"Ayan",
""
],
[
"Tangphati",
"Takol",
""
],
[
"Pradhan",
"Anirudh",
""
]
] | We explore the existence of wormholes in the context of $f(R,T)$ gravity. The $f(R,T)$ theory is a curvature-matter coupled modified gravity that depends on an arbitrary function of the Ricci scalar $R$ and the trace of the stress-energy tensor $T$. In this work, we adopt two different choices for the matter Lagrangian density ($\mathcal{L}_m= \mathcal{P}$ and $\mathcal{L}_m= p_r$) and investigate the impact of each one on wormhole structure. By adequately specifying the redshift function and the shape function, we found a variety of exact wormhole solutions in the theory. Our finding indicates that, for both classes of wormholes the energy density is always positive throughout the spacetime, while the radial pressure is negative. This means exotic matter is necessary for the existence of wormholes in $f(R,T)$ gravity. |
1009.1838 | Holger M\"uller | Holger Mueller, Achim Peters, and Steven Chu | Reply to: Atom gravimeters and the gravitational redshift | Reply to P. Wolf et al., arXiv:1009.0602 | Nature 467:E2,2010 | 10.1038/nature09341 | null | gr-qc physics.atom-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We stand by our result [H. Mueller et al., Nature 463, 926-929 (2010)]. The
comment [P. Wolf et al., Nature 467, E1 (2010)] revisits an interesting issue
that has been known for decades, the relationship between test of the
universality of free fall and redshift experiments. However, it arrives at its
conclusions by applying the laws of physics that are questioned by redshift
experiments; this precludes the existence of measurable signals. Since this
issue applies to all classical redshift tests as well as atom interferometry
redshift tests, these experiments are equivalent in all aspects in question.
| [
{
"created": "Thu, 9 Sep 2010 18:05:49 GMT",
"version": "v1"
}
] | 2010-11-15 | [
[
"Mueller",
"Holger",
""
],
[
"Peters",
"Achim",
""
],
[
"Chu",
"Steven",
""
]
] | We stand by our result [H. Mueller et al., Nature 463, 926-929 (2010)]. The comment [P. Wolf et al., Nature 467, E1 (2010)] revisits an interesting issue that has been known for decades, the relationship between test of the universality of free fall and redshift experiments. However, it arrives at its conclusions by applying the laws of physics that are questioned by redshift experiments; this precludes the existence of measurable signals. Since this issue applies to all classical redshift tests as well as atom interferometry redshift tests, these experiments are equivalent in all aspects in question. |
2303.11134 | Leihua Liu | Ke Gao, Lei-Hua Liu | Microlensing and event rate of static spherically symmetric wormhole | Significantly improved | null | null | null | gr-qc astro-ph.GA | http://creativecommons.org/licenses/by/4.0/ | Since the lensing effects play a vital role in modern cosmology. A new
framework is developed for the static spherically symmetrical wormhole (WH) in
terms of the radial equation of state (REoS). Following the standard procedure,
we calculate the lensing equation, magnification, and event rate according to
REoS, where our analysis indicates that the image problem of light source is
complicated. As for the event rate, our investigations indicate that the larger
values for the throat radius of WH and REoS will lead to larger values of the
event rate. Compared with the event rate of blackhole, it is also claimed that
the value of WH will be larger, in which their mass and the distance of them
(blackhole or WH) between the light source and observer are comparable. Thus,
our study could provide a possibility for distinguishing the WH and blackhole
under similar circumstances.
| [
{
"created": "Mon, 20 Mar 2023 14:11:55 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Jun 2023 12:40:10 GMT",
"version": "v2"
},
{
"created": "Mon, 12 Jun 2023 03:27:21 GMT",
"version": "v3"
},
{
"created": "Mon, 9 Oct 2023 13:36:21 GMT",
"version": "v4"
}
] | 2023-10-10 | [
[
"Gao",
"Ke",
""
],
[
"Liu",
"Lei-Hua",
""
]
] | Since the lensing effects play a vital role in modern cosmology. A new framework is developed for the static spherically symmetrical wormhole (WH) in terms of the radial equation of state (REoS). Following the standard procedure, we calculate the lensing equation, magnification, and event rate according to REoS, where our analysis indicates that the image problem of light source is complicated. As for the event rate, our investigations indicate that the larger values for the throat radius of WH and REoS will lead to larger values of the event rate. Compared with the event rate of blackhole, it is also claimed that the value of WH will be larger, in which their mass and the distance of them (blackhole or WH) between the light source and observer are comparable. Thus, our study could provide a possibility for distinguishing the WH and blackhole under similar circumstances. |
gr-qc/0304052 | Igor Novikov | Igor D. Novikov | Developments in General Relativity: Black Hole Singularity and Beyond | 13 pages | null | 10.1142/9789812704009_0008 | null | gr-qc | null | At the 20-th Texas Symposium on Relativistic Astrophysics there was a plenary
talk devoted to the recent developments in classical Relativity. In that talk
the problems of gravitational collapse, collisions of black holes, and of black
holes as celestial bodies were discussed. But probably the problems of the
internal structure of black holes are a real great challenge. In my talk I want
to outline the recent achievements in our understanding of the nature of the
singularity (and beyond!) inside a realistic rotating black hole. This
presentation also addresses the following questions: Can we see what happens
inside a black hole? Can a falling observer cross the singularity without being
crushed? An answer to these questions is probably "yes".
| [
{
"created": "Mon, 14 Apr 2003 12:24:13 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Apr 2003 17:35:14 GMT",
"version": "v2"
}
] | 2017-08-23 | [
[
"Novikov",
"Igor D.",
""
]
] | At the 20-th Texas Symposium on Relativistic Astrophysics there was a plenary talk devoted to the recent developments in classical Relativity. In that talk the problems of gravitational collapse, collisions of black holes, and of black holes as celestial bodies were discussed. But probably the problems of the internal structure of black holes are a real great challenge. In my talk I want to outline the recent achievements in our understanding of the nature of the singularity (and beyond!) inside a realistic rotating black hole. This presentation also addresses the following questions: Can we see what happens inside a black hole? Can a falling observer cross the singularity without being crushed? An answer to these questions is probably "yes". |
gr-qc/0303005 | Pal G. Molnar | Pal G. Molnar and Klaus Elsasser | Uniqueness of the electrostatic solution in Schwarzschild space | 3 pages, no figures, uses revtex4 style files | Phys.Rev.D67:047501,2003 | 10.1103/PhysRevD.67.047501 | null | gr-qc math-ph math.MP | null | In this Brief Report we give the proof that the solution of any static test
charge distribution in Schwarzschild space is unique. In order to give the
proof we derive the first Green's identity written with p-forms on (pseudo)
Riemannian manifolds. Moreover, the proof of uniqueness can be shown for either
any purely electric or purely magnetic field configuration. The spacetime
geometry is not crucial for the proof.
| [
{
"created": "Sun, 2 Mar 2003 10:22:22 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Molnar",
"Pal G.",
""
],
[
"Elsasser",
"Klaus",
""
]
] | In this Brief Report we give the proof that the solution of any static test charge distribution in Schwarzschild space is unique. In order to give the proof we derive the first Green's identity written with p-forms on (pseudo) Riemannian manifolds. Moreover, the proof of uniqueness can be shown for either any purely electric or purely magnetic field configuration. The spacetime geometry is not crucial for the proof. |
1905.04860 | Yong-Wan Kim | Soon-Tae Hong, Yong-Wan Kim, Young-Jai Park | GEMS embeddings and freely falling temperatures of Schwarzschild(-AdS)
black holes in massive gravity | 15 pages, 7 figures, title changed, references added, version to
appear in PLB. arXiv admin note: text overlap with arXiv:1812.00373 | null | 10.1016/j.physletb.2019.135116 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We globally embed (3+1)-dimensional Schwarzschild and Schwarzschild-AdS black
holes in massive gravity into (5+2)-dimensional flat spacetimes. Making use of
embedding coordinates, we directly obtain the generalized Hawking, Unruh and
freely falling temperatures in a Schwarzschild and Schwarzschild-AdS black hole
due to massive graviton effects.
| [
{
"created": "Mon, 13 May 2019 05:07:44 GMT",
"version": "v1"
},
{
"created": "Thu, 16 May 2019 07:17:14 GMT",
"version": "v2"
},
{
"created": "Wed, 27 Nov 2019 07:47:53 GMT",
"version": "v3"
}
] | 2019-12-02 | [
[
"Hong",
"Soon-Tae",
""
],
[
"Kim",
"Yong-Wan",
""
],
[
"Park",
"Young-Jai",
""
]
] | We globally embed (3+1)-dimensional Schwarzschild and Schwarzschild-AdS black holes in massive gravity into (5+2)-dimensional flat spacetimes. Making use of embedding coordinates, we directly obtain the generalized Hawking, Unruh and freely falling temperatures in a Schwarzschild and Schwarzschild-AdS black hole due to massive graviton effects. |
gr-qc/0309034 | Pantelis Apostolopoulos | Michael Tsamparlis and Pantelis S. Apostolopoulos | Ricci and matter collineations of locally rotationally symmetric
space-times | 21 pages, Latex; to appear in General Relativity and Gravitation | Gen.Rel.Grav. 36 (2004) 47-69 | 10.1023/B:GERG.0000006693.75816.e9 | null | gr-qc | null | A new method is presented for the determination of Ricci Collineations (RC)
and Matter Collineations (MC) of a given spacetime, in the cases where the
Ricci tensor and the energy momentum tensor are non-degenerate and have a
similar form with the metric. This method reduces the problem of finding the
RCs and the MCs to that of determining the KVs whereas at the same time uses
already known results on the motions of the metric. We employ this method to
determine all hypersurface homogeneous locally rotationally symmetric
spacetimes, which admit proper RCs and MCs. We also give the corresponding
collineation vectors.
| [
{
"created": "Fri, 5 Sep 2003 15:34:50 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Tsamparlis",
"Michael",
""
],
[
"Apostolopoulos",
"Pantelis S.",
""
]
] | A new method is presented for the determination of Ricci Collineations (RC) and Matter Collineations (MC) of a given spacetime, in the cases where the Ricci tensor and the energy momentum tensor are non-degenerate and have a similar form with the metric. This method reduces the problem of finding the RCs and the MCs to that of determining the KVs whereas at the same time uses already known results on the motions of the metric. We employ this method to determine all hypersurface homogeneous locally rotationally symmetric spacetimes, which admit proper RCs and MCs. We also give the corresponding collineation vectors. |
1810.01948 | Stanley Deser | S. Deser | A note on matter covariantization for gravity coupling | Published version, typos corrected | Gen Relativ Gravit (2019) 51: 18 | 10.1007/s10714-018-2498-6 | BRX-6639; Calt-TH 2018-039 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Covariantization is of course required for initially flat space matter to
couple consistently to GR; here I show in detail for concrete systems how it
follows in the same physical way as that deriving GR itself from its initial
free-field form.
| [
{
"created": "Wed, 3 Oct 2018 20:29:58 GMT",
"version": "v1"
},
{
"created": "Sat, 5 Jan 2019 19:05:37 GMT",
"version": "v2"
}
] | 2019-01-16 | [
[
"Deser",
"S.",
""
]
] | Covariantization is of course required for initially flat space matter to couple consistently to GR; here I show in detail for concrete systems how it follows in the same physical way as that deriving GR itself from its initial free-field form. |
2210.04004 | Thomas Buchert | Ismael Delgado Gaspar, Thomas Buchert, Jan J. Ostrowski | Beyond relativistic Lagrangian perturbation theory. I. An exact-solution
controlled model for structure formation | 21 pages, 4 figures, matches published version in PRD | Phys. Rev. D 107, 024018 (2023) | 10.1103/PhysRevD.107.024018 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We develop a new nonlinear method to model structure formation in general
relativity from a generalization of the relativistic Lagrangian perturbation
schemes, controlled by Szekeres (and LTB) exact solutions. The overall approach
can be interpreted as the evolution of a deformation field on an inhomogeneous
reference model, obeying locally Friedmann-like equations. In the special case
of locally one-dimensional deformations, the new model contains the entire
Szekeres family of exact solutions. As thus formulated, this approach
paraphrases the Newtonian and relativistic Zel'dovich approximations, having a
large potential for applications in contexts where relativistic degrees of
freedom are relevant. Numerical simulations are implemented to illustrate the
capabilities and accuracy of the model.
| [
{
"created": "Sat, 8 Oct 2022 12:01:39 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Jan 2023 11:41:02 GMT",
"version": "v2"
}
] | 2023-01-19 | [
[
"Gaspar",
"Ismael Delgado",
""
],
[
"Buchert",
"Thomas",
""
],
[
"Ostrowski",
"Jan J.",
""
]
] | We develop a new nonlinear method to model structure formation in general relativity from a generalization of the relativistic Lagrangian perturbation schemes, controlled by Szekeres (and LTB) exact solutions. The overall approach can be interpreted as the evolution of a deformation field on an inhomogeneous reference model, obeying locally Friedmann-like equations. In the special case of locally one-dimensional deformations, the new model contains the entire Szekeres family of exact solutions. As thus formulated, this approach paraphrases the Newtonian and relativistic Zel'dovich approximations, having a large potential for applications in contexts where relativistic degrees of freedom are relevant. Numerical simulations are implemented to illustrate the capabilities and accuracy of the model. |
1508.05303 | Giuseppe Papallo | Giuseppe Papallo and Harvey S. Reall | Graviton time delay and a speed limit for small black holes in
Einstein-Gauss-Bonnet theory | v2: Typos corrected. Short argument for time advance added in section
4.4. Added reference. Matches the version to appear in JHEP. 22 pages +
appendices, 15 figures | JHEP 11 (2015) 109 | 10.1007/JHEP11(2015)109 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Camanho, Edelstein, Maldacena and Zhiboedov have shown that gravitons can
experience a negative Shapiro time delay, i.e. a time advance, in
Einstein-Gauss-Bonnet theory. They studied gravitons propagating in singular
"shock-wave" geometries. We study this effect for gravitons propagating in
smooth black hole spacetimes. For a small enough black hole, we find that
gravitons of appropriate polarisation, and small impact parameter, can
experience time advance. Such gravitons can also exhibit a deflection angle
less than $\pi$, characteristic of a repulsive short-distance gravitational
interaction. We discuss problems with the suggestion that the time advance can
be used to build a "time machine". In particular, we argue that a small black
hole cannot be boosted to a speed arbitrarily close to the speed of light, as
would be required in such a construction.
| [
{
"created": "Fri, 21 Aug 2015 15:11:33 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Oct 2015 14:22:05 GMT",
"version": "v2"
}
] | 2015-11-24 | [
[
"Papallo",
"Giuseppe",
""
],
[
"Reall",
"Harvey S.",
""
]
] | Camanho, Edelstein, Maldacena and Zhiboedov have shown that gravitons can experience a negative Shapiro time delay, i.e. a time advance, in Einstein-Gauss-Bonnet theory. They studied gravitons propagating in singular "shock-wave" geometries. We study this effect for gravitons propagating in smooth black hole spacetimes. For a small enough black hole, we find that gravitons of appropriate polarisation, and small impact parameter, can experience time advance. Such gravitons can also exhibit a deflection angle less than $\pi$, characteristic of a repulsive short-distance gravitational interaction. We discuss problems with the suggestion that the time advance can be used to build a "time machine". In particular, we argue that a small black hole cannot be boosted to a speed arbitrarily close to the speed of light, as would be required in such a construction. |
1908.09769 | Babak Vakili | Fatimah Tavakoli and Babak Vakili | Bianchi type I, Schutz perfect fluid and evolutionary quantum cosmology | 14 pages, 2 figures | Gen. Rel. Grav. 51 (2019) 122 | 10.1007/s10714-019-2602-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the classical and quantum cosmology of a universe in which the
matter content is a perfect fluid and the background geometry is described by a
Bianchi type I metric. To write the Hamiltonian of the perfect fluid we use the
Schutz representation, in terms of which, after a particular gauge fixing, we
are led to an identification of a clock parameter which may play the role of
time for the corresponding dynamical system. In view of the classical
cosmology, it is shown that the evolution of the universe represents a late
time expansion coming from a big-bang singularity. We also consider the issue
of quantum cosmology in the framework of the canonical Wheeler-DeWitt (WDW)
equation. It is shown that the Schutz formalism leads to the introduction of a
momentum that enters linearly into Hamiltonian. This means that the WDW
equation takes the form of a Schr\"{o}dinger equation for the
quantum-mechanical description of the model under consideration. We find the
eigenfunctions and with the use of them construct the closed form expressions
for the wave functions of the universe. By means of the resulting wave function
we evaluate the expectation values and investigate the possibility of the
avoidance of classical singularities due to quantum effects. We also look at
the problem through Bohmian approach of quantum mechanics and while recovering
the quantum solutions, we deal with the reason of the singularity avoidance by
introducing quantum potential.
| [
{
"created": "Mon, 26 Aug 2019 16:10:40 GMT",
"version": "v1"
}
] | 2019-09-23 | [
[
"Tavakoli",
"Fatimah",
""
],
[
"Vakili",
"Babak",
""
]
] | We study the classical and quantum cosmology of a universe in which the matter content is a perfect fluid and the background geometry is described by a Bianchi type I metric. To write the Hamiltonian of the perfect fluid we use the Schutz representation, in terms of which, after a particular gauge fixing, we are led to an identification of a clock parameter which may play the role of time for the corresponding dynamical system. In view of the classical cosmology, it is shown that the evolution of the universe represents a late time expansion coming from a big-bang singularity. We also consider the issue of quantum cosmology in the framework of the canonical Wheeler-DeWitt (WDW) equation. It is shown that the Schutz formalism leads to the introduction of a momentum that enters linearly into Hamiltonian. This means that the WDW equation takes the form of a Schr\"{o}dinger equation for the quantum-mechanical description of the model under consideration. We find the eigenfunctions and with the use of them construct the closed form expressions for the wave functions of the universe. By means of the resulting wave function we evaluate the expectation values and investigate the possibility of the avoidance of classical singularities due to quantum effects. We also look at the problem through Bohmian approach of quantum mechanics and while recovering the quantum solutions, we deal with the reason of the singularity avoidance by introducing quantum potential. |
1703.03059 | Peter K.F. Kuhfittig | Peter K.F. Kuhfittig and Vance D. Gladney | Noncommutative-geometry inspired charged wormholes with low tidal forces | 8 pages, no figures | Journal of Applied Mathematics and Physics (JAMP), vol. 5, pp.
574-581 (2017) | 10.4236/jamp.2017.53049 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When Morris and Thorne first proposed that wormholes might be actual physical
structures suitable for interstellar travel, they needed to pay close attention
to certain traversability conditions such as low tidal forces, which placed
severe constraints on the wormhole geometry. Even more problematical was the
need for "exotic matter" resulting from the unavoidable violation of the null
energy condition required to hold a wormhole open. The purpose of this paper is
to overcome these problems by starting with the charged wormhole model of Kim
and Lee and assuming a noncommutative-geometry background: the violation of the
null energy condition can be attributed to the latter, while the electric
charge allows the reduction of the tidal forces to acceptable levels without
invoking the trivial zero-tidal-force assumption.
| [
{
"created": "Wed, 8 Mar 2017 22:23:16 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Jul 2024 00:24:06 GMT",
"version": "v2"
}
] | 2024-07-15 | [
[
"Kuhfittig",
"Peter K. F.",
""
],
[
"Gladney",
"Vance D.",
""
]
] | When Morris and Thorne first proposed that wormholes might be actual physical structures suitable for interstellar travel, they needed to pay close attention to certain traversability conditions such as low tidal forces, which placed severe constraints on the wormhole geometry. Even more problematical was the need for "exotic matter" resulting from the unavoidable violation of the null energy condition required to hold a wormhole open. The purpose of this paper is to overcome these problems by starting with the charged wormhole model of Kim and Lee and assuming a noncommutative-geometry background: the violation of the null energy condition can be attributed to the latter, while the electric charge allows the reduction of the tidal forces to acceptable levels without invoking the trivial zero-tidal-force assumption. |
1108.0449 | Ariel Edery | Hugues Beauchesne and Ariel Edery | Emergence of thin shell structure during collapse in isotropic
coordinates | 24 pages, 10 figures. version to appear in Phys. Rev. D | Phys. Rev. D 85, 044056 (2012) | 10.1103/PhysRevD.85.044056 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Numerical studies of gravitational collapse in isotropic coordinates have
recently shown an interesting connection between the gravitational Lagrangian
and black hole thermodynamics. A study of the actual spacetime was not the main
focus of this work and in particular, the rich and interesting structure of the
interior has not been investigated in much detail and remains largely unknown.
We elucidate its features by performing a numerical study of the spacetime in
isotropic coordinates during gravitational collapse of a massless scalar field.
The most salient feature to emerge is the formation of a thin shell of matter
just inside the apparent horizon. The energy density and Ricci scalar peak at
the shell and there is a jump discontinuity in the extrinsic curvature across
the apparent horizon, the hallmark that a thin shell is present in its
vicinity. At late stages of the collapse, the spacetime consists of two vacuum
regions separated by the thin shell. The interior is described by an
interesting collapsing isotropic universe. It tends towards a vacuum (never
reaches a perfect vacuum) and there is a slight inhomogeneity in the interior
that plays a crucial role in the collapse process as the areal radius tends to
zero. The spacetime evolves towards a curvature (physical) singularity in the
interior, both a Weyl and Ricci singularity. In the exterior, our numerical
results match closely the analytical form of the Schwarzschild metric in
isotropic coordinates, providing a strong test of our numerical code.
| [
{
"created": "Tue, 2 Aug 2011 00:03:28 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Feb 2012 22:08:51 GMT",
"version": "v2"
}
] | 2012-02-24 | [
[
"Beauchesne",
"Hugues",
""
],
[
"Edery",
"Ariel",
""
]
] | Numerical studies of gravitational collapse in isotropic coordinates have recently shown an interesting connection between the gravitational Lagrangian and black hole thermodynamics. A study of the actual spacetime was not the main focus of this work and in particular, the rich and interesting structure of the interior has not been investigated in much detail and remains largely unknown. We elucidate its features by performing a numerical study of the spacetime in isotropic coordinates during gravitational collapse of a massless scalar field. The most salient feature to emerge is the formation of a thin shell of matter just inside the apparent horizon. The energy density and Ricci scalar peak at the shell and there is a jump discontinuity in the extrinsic curvature across the apparent horizon, the hallmark that a thin shell is present in its vicinity. At late stages of the collapse, the spacetime consists of two vacuum regions separated by the thin shell. The interior is described by an interesting collapsing isotropic universe. It tends towards a vacuum (never reaches a perfect vacuum) and there is a slight inhomogeneity in the interior that plays a crucial role in the collapse process as the areal radius tends to zero. The spacetime evolves towards a curvature (physical) singularity in the interior, both a Weyl and Ricci singularity. In the exterior, our numerical results match closely the analytical form of the Schwarzschild metric in isotropic coordinates, providing a strong test of our numerical code. |
1707.03284 | Satadal Datta | Satadal Datta | Analogue tachyon in Jeans Cloud | null | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the linear perturbations in a stable Jeans cloud, i.e; the dimension
of the cloud is less than the Jeans length. We find that the linear
perturbation of density in such a system obeys a wave equation in acoustic
analogue of Minkowski space-time which is similar to Klein-Gordon equation for
tachyon field in Minkowski space-time, i.e; Klein-Gordon equation with negative
mass-squared term in a flat space time background. We further find the analogy
with tachyon field for linear perturbation of density by studying linear
perturbations in a stable cloud made of Bose-Einstein condensate as dark
matter.
| [
{
"created": "Sun, 9 Jul 2017 14:21:15 GMT",
"version": "v1"
}
] | 2017-07-12 | [
[
"Datta",
"Satadal",
""
]
] | We study the linear perturbations in a stable Jeans cloud, i.e; the dimension of the cloud is less than the Jeans length. We find that the linear perturbation of density in such a system obeys a wave equation in acoustic analogue of Minkowski space-time which is similar to Klein-Gordon equation for tachyon field in Minkowski space-time, i.e; Klein-Gordon equation with negative mass-squared term in a flat space time background. We further find the analogy with tachyon field for linear perturbation of density by studying linear perturbations in a stable cloud made of Bose-Einstein condensate as dark matter. |
1904.06914 | Rajani K.V | Rajani K.V., C.L. Ahmed Rizwan, A. Naveena Kumara, Deepak Vaid, Ajith
K.M | Regular Bardeen AdS Black Hole as a Heat Engine | null | Nucl.Phys.B 960 (2020) 115166 | 10.1016/j.nuclphysb.2020.115166 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the thermodynamic phase transitions and heat engine efficiency
in regular Bardeen AdS black hole. Interpreting cosmological constant as
thermodynamic pressure, we study the thermodynamics using T S and P v plots.
Specific heat studies also carried out in detail. A first order phase
transition in evident from these studies. These are followed by the
construction of a heat engine considering the black hole as working substance.
The efficiency is obtained via a thermodynamic cycle in the P V plane which
receives and ejects heat. The heat engine efficiency is improved by adding a
quintessence field. The analytical expression for heat engine efficiency is
derived in terms of quintessence dark energy parameter. This result may deepen
our understanding about thermodynamics of asymptotically AdS black holes.
| [
{
"created": "Mon, 15 Apr 2019 09:02:30 GMT",
"version": "v1"
}
] | 2020-09-21 | [
[
"V.",
"Rajani K.",
""
],
[
"Rizwan",
"C. L. Ahmed",
""
],
[
"Kumara",
"A. Naveena",
""
],
[
"Vaid",
"Deepak",
""
],
[
"M",
"Ajith K.",
""
]
] | We investigate the thermodynamic phase transitions and heat engine efficiency in regular Bardeen AdS black hole. Interpreting cosmological constant as thermodynamic pressure, we study the thermodynamics using T S and P v plots. Specific heat studies also carried out in detail. A first order phase transition in evident from these studies. These are followed by the construction of a heat engine considering the black hole as working substance. The efficiency is obtained via a thermodynamic cycle in the P V plane which receives and ejects heat. The heat engine efficiency is improved by adding a quintessence field. The analytical expression for heat engine efficiency is derived in terms of quintessence dark energy parameter. This result may deepen our understanding about thermodynamics of asymptotically AdS black holes. |
1801.09660 | Hussain Gohar | Ana Alonso-Serrano, Mariusz P. Dabrowski, Hussain Gohar | Generalized uncertainty principle impact onto the black holes
information flux and the sparsity of Hawking radiation | 6 pages, 2 figures, typos corrected, published in Phys. Rev. D | Phys. Rev. D 97, 044029 (2018) | 10.1103/PhysRevD.97.044029 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the generalized uncertainty principle (GUP) corrections to the
entropy content and the information flux of black holes, as well as the
corrections to the sparsity of the Hawking radiation at the late stages of
evaporation. We find that due to these quantum gravity motivated corrections,
the entropy flow per particle reduces its value on the approach to the Planck
scale due to a better accuracy in counting the number of microstates. We also
show that the radiation flow is no longer sparse when the mass of a black hole
approaches Planck mass which is not the case for non-GUP calculations.
| [
{
"created": "Mon, 29 Jan 2018 18:36:26 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Feb 2018 13:56:02 GMT",
"version": "v2"
},
{
"created": "Thu, 22 Feb 2018 16:26:07 GMT",
"version": "v3"
}
] | 2018-02-23 | [
[
"Alonso-Serrano",
"Ana",
""
],
[
"Dabrowski",
"Mariusz P.",
""
],
[
"Gohar",
"Hussain",
""
]
] | We investigate the generalized uncertainty principle (GUP) corrections to the entropy content and the information flux of black holes, as well as the corrections to the sparsity of the Hawking radiation at the late stages of evaporation. We find that due to these quantum gravity motivated corrections, the entropy flow per particle reduces its value on the approach to the Planck scale due to a better accuracy in counting the number of microstates. We also show that the radiation flow is no longer sparse when the mass of a black hole approaches Planck mass which is not the case for non-GUP calculations. |
1407.8237 | Luca Fabbri | Luca Fabbri, Stefano Vignolo | ELKO and Dirac Spinors seen from Torsion | 11 pages | Int.J.Mod.Phys.D23:1444001(2014) | 10.1142/S0218271814440015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, the recently-introduced ELKO and the well-known Dirac spinor
fields will be compared; however, instead of comparing them under the point of
view of their algebraic properties or their dynamical features, we will proceed
by investigating the analogies and similarities in terms of their geometrical
character viewed from the perspective of torsion. The paper will be concluded
by sketching some consequences for the application to cosmology and particle
physics.
| [
{
"created": "Wed, 30 Jul 2014 23:40:43 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Sep 2014 16:54:43 GMT",
"version": "v2"
}
] | 2014-09-12 | [
[
"Fabbri",
"Luca",
""
],
[
"Vignolo",
"Stefano",
""
]
] | In this paper, the recently-introduced ELKO and the well-known Dirac spinor fields will be compared; however, instead of comparing them under the point of view of their algebraic properties or their dynamical features, we will proceed by investigating the analogies and similarities in terms of their geometrical character viewed from the perspective of torsion. The paper will be concluded by sketching some consequences for the application to cosmology and particle physics. |
1712.08031 | Francesco Becattini | F. Becattini (University of Florence and INFN) | Thermodynamic equilibrium with acceleration and the Unruh effect | 15 pages, 2 figures; updated version accepted for publication in
Phys. Rev. D | Phys. Rev. D 97, 085013 (2018) | 10.1103/PhysRevD.97.085013 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We address the problem of thermodynamic equilibrium with constant
acceleration along the velocity field lines in a quantum relativistic
statistical mechanics framework. We show that for a free scalar quantum field,
after vacuum subtraction, all mean values vanish when the local temperature T
is as low as the Unruh temperature T_U = A/2\pi where A is the magnitude of the
acceleration four-vector. We argue that the Unruh temperature is an absolute
lower bound for the temperature of any accelerated fluid at global
thermodynamic equilibrium. We discuss the conditions of this bound to be
applicable in a local thermodynamic equilibrium situation.
| [
{
"created": "Thu, 21 Dec 2017 15:54:22 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Mar 2018 12:21:03 GMT",
"version": "v2"
}
] | 2018-04-25 | [
[
"Becattini",
"F.",
"",
"University of Florence and INFN"
]
] | We address the problem of thermodynamic equilibrium with constant acceleration along the velocity field lines in a quantum relativistic statistical mechanics framework. We show that for a free scalar quantum field, after vacuum subtraction, all mean values vanish when the local temperature T is as low as the Unruh temperature T_U = A/2\pi where A is the magnitude of the acceleration four-vector. We argue that the Unruh temperature is an absolute lower bound for the temperature of any accelerated fluid at global thermodynamic equilibrium. We discuss the conditions of this bound to be applicable in a local thermodynamic equilibrium situation. |
gr-qc/0203091 | Laszlo A. Gergely | L\'aszl\'o \'A. Gergely, Zolt\'an Perj\'es | Vacuum Kerr-Schild metrics generated by nontwisting congruences | 12 pages | Annalen Phys. 3 (1994) 609-619 | 10.1002/andp.19945060706 | null | gr-qc | null | The Kerr-Schild pencil of metrics $\tilde g_{ab}=g_{ab}+V l_al_b$, with
$g_{ab}$ and $\tilde g_{ab}$ satisfying the vacuum Einstein equations, is
investigated in the case when the null vector $l$ has vanishing twist. This
class of Kerr-Schild metrics contains two solutions: the Kasner metric and a
metric wich can be obtained from the Kasner metric by a complex coordinate
transformation. Both are limiting cases of the K\'ota-Perj\'es metrics. The
base space-time is a pp-wave.
| [
{
"created": "Tue, 26 Mar 2002 12:39:23 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Gergely",
"László Á.",
""
],
[
"Perjés",
"Zoltán",
""
]
] | The Kerr-Schild pencil of metrics $\tilde g_{ab}=g_{ab}+V l_al_b$, with $g_{ab}$ and $\tilde g_{ab}$ satisfying the vacuum Einstein equations, is investigated in the case when the null vector $l$ has vanishing twist. This class of Kerr-Schild metrics contains two solutions: the Kasner metric and a metric wich can be obtained from the Kasner metric by a complex coordinate transformation. Both are limiting cases of the K\'ota-Perj\'es metrics. The base space-time is a pp-wave. |
gr-qc/9907007 | Ken D. Olum | Ken D. Olum | The Ori-Soen time machine | 5 pages, RevTeX, 7 figures with epsf, miscellaneous clarifications in
v2, minor updates to correspond to version to appear in PRD | Phys.Rev. D61 (2000) 124022 | 10.1103/PhysRevD.61.124022 | null | gr-qc | null | Ori and Soen have proposed a spacetime which has closed causal curves on the
boundary of a region of normal causality, all within a region where the weak
energy condition (positive energy density) is satisfied. I analyze the causal
structure of this spacetime in some simplified models, show that the Cauchy
horizon is compactly generated, and argue that any attempt to build such a
spacetime with normal matter might lead to singular behavior where the
causality violation would otherwise take place.
| [
{
"created": "Fri, 2 Jul 1999 21:14:25 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Dec 1999 21:26:51 GMT",
"version": "v2"
},
{
"created": "Tue, 18 Apr 2000 21:41:05 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Olum",
"Ken D.",
""
]
] | Ori and Soen have proposed a spacetime which has closed causal curves on the boundary of a region of normal causality, all within a region where the weak energy condition (positive energy density) is satisfied. I analyze the causal structure of this spacetime in some simplified models, show that the Cauchy horizon is compactly generated, and argue that any attempt to build such a spacetime with normal matter might lead to singular behavior where the causality violation would otherwise take place. |
2201.06683 | Chikun Ding | Chikun Ding, Yu Shi, Jun Chen, Yuebing Zhou and Changqing Liu | High dimensional AdS-like black hole and Phase transition in
Einstein-bumblebee gravity | 19 pages,four figures, 1 table | Chin. Phys. C 47 045102 (2023) | 10.1088/1674-1137/aca8f4 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper we obtain an exact high dimensional anti-de Sitter (AdS) black
hole solution in Einstein-bumblebee gravity theory. This AdS-like black hole
can only exist with a linear functional potential of the bumblebee field. We
find that the Smarr formula and the first law of black hole thermodynamics can
still be constructed in this Lorentz symmetry breaking black hole spacetime as
long as its temperature, entropy and volume are slightly modified. We find also
that there exist two kinds of phase transition: small-large black hole phase
transition and Hawking-Page phase transition, like those of Schwarzschild AdS
black hole. After Lorentz symmetry breaking, the black hole mass at divergent
point of heat capacity becomes small, and the Gibbs free energy of the
meta-stable large black hole is also smaller, showing that the large stable
black hole can be more easily formed.
| [
{
"created": "Tue, 18 Jan 2022 01:08:43 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Sep 2022 07:34:28 GMT",
"version": "v2"
}
] | 2023-02-27 | [
[
"Ding",
"Chikun",
""
],
[
"Shi",
"Yu",
""
],
[
"Chen",
"Jun",
""
],
[
"Zhou",
"Yuebing",
""
],
[
"Liu",
"Changqing",
""
]
] | In this paper we obtain an exact high dimensional anti-de Sitter (AdS) black hole solution in Einstein-bumblebee gravity theory. This AdS-like black hole can only exist with a linear functional potential of the bumblebee field. We find that the Smarr formula and the first law of black hole thermodynamics can still be constructed in this Lorentz symmetry breaking black hole spacetime as long as its temperature, entropy and volume are slightly modified. We find also that there exist two kinds of phase transition: small-large black hole phase transition and Hawking-Page phase transition, like those of Schwarzschild AdS black hole. After Lorentz symmetry breaking, the black hole mass at divergent point of heat capacity becomes small, and the Gibbs free energy of the meta-stable large black hole is also smaller, showing that the large stable black hole can be more easily formed. |
2406.02288 | David Gr\"uber | D. Gr\"uber, P. P. Avelino, L. Sousa | Domain walls in light of Cosmic Microwave Background and Pulsar Timing
Array data | null | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper, we study the compatibility of biased domain wall scenarios
with current gravitational wave data. We show that the Cosmic Microwave
Background bounds on the fractional density of gravitational waves at the time
of decoupling may only slightly improve on the constraints that result from
requiring that domain walls never dominate the cosmic energy budget. We show
that, despite this, the range of energy scales of the domain-wall forming phase
transitions are already quite constricted, even if the networks decay early in
cosmological history. We also show that, if domain walls are to provide an
explanation to the stochastic gravitational wave background that was recently
detected by pulsar timing arrays, they not only have to decay early in the
radiation dominated era but also their energy density would have to be close to
dominating the energy density of the universe, which would require some fine
tuning of the parameters of the models.
| [
{
"created": "Tue, 4 Jun 2024 13:01:20 GMT",
"version": "v1"
}
] | 2024-06-05 | [
[
"Grüber",
"D.",
""
],
[
"Avelino",
"P. P.",
""
],
[
"Sousa",
"L.",
""
]
] | In this paper, we study the compatibility of biased domain wall scenarios with current gravitational wave data. We show that the Cosmic Microwave Background bounds on the fractional density of gravitational waves at the time of decoupling may only slightly improve on the constraints that result from requiring that domain walls never dominate the cosmic energy budget. We show that, despite this, the range of energy scales of the domain-wall forming phase transitions are already quite constricted, even if the networks decay early in cosmological history. We also show that, if domain walls are to provide an explanation to the stochastic gravitational wave background that was recently detected by pulsar timing arrays, they not only have to decay early in the radiation dominated era but also their energy density would have to be close to dominating the energy density of the universe, which would require some fine tuning of the parameters of the models. |
1408.4839 | Mauricio Bellini | Ricardo Aguila, Jos\'e Edgar Madriz Aguilar, Claudia Moreno (CUCEI,
Guadalajara University), Mauricio Bellini (IFIMAR, CONICET and UNMdP) | Present accelerated expansion of the universe from new Weyl-Integrable
gravity approach | Version to be published in Eur. Phys. J. C | null | 10.1140/epjc/s10052-014-3158-y | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate if a recently introduced formulation of general relativity on
a Weyl-integrable geometry, contains cosmological solutions exhibiting
acceleration in the present cosmic expansion. We derive the general conditions
to have acceleration in the expansion of the universe and obtain a particular
solution for the Weyl scalar field describing a cosmological model for the
present time in concordance with the data combination Planck + WP + BAO + SN.
| [
{
"created": "Wed, 20 Aug 2014 23:43:47 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Oct 2014 15:03:54 GMT",
"version": "v2"
},
{
"created": "Fri, 7 Nov 2014 15:43:27 GMT",
"version": "v3"
}
] | 2015-06-22 | [
[
"Aguila",
"Ricardo",
"",
"CUCEI,\n Guadalajara University"
],
[
"Aguilar",
"José Edgar Madriz",
"",
"CUCEI,\n Guadalajara University"
],
[
"Moreno",
"Claudia",
"",
"CUCEI,\n Guadalajara University"
],
[
"Bellini",
"Mauricio",
"",
"IFIMAR, CONICET and UNMdP"
]
] | We investigate if a recently introduced formulation of general relativity on a Weyl-integrable geometry, contains cosmological solutions exhibiting acceleration in the present cosmic expansion. We derive the general conditions to have acceleration in the expansion of the universe and obtain a particular solution for the Weyl scalar field describing a cosmological model for the present time in concordance with the data combination Planck + WP + BAO + SN. |
gr-qc/9510004 | Contreras Gerardo | R. Bertolotti, G. Contreras, L. A. N\'u\~nez, U. Percoco (University
of Los Andes, M\`erida, Venezuela) and J.Carot (Universitat de les Illes
Baleares, Mallorca, Espa\~na) | Comment on Ricci Collineations of Static Spherically Symmetric
Spacetimes | 4 pages,LaTex file | J.Math.Phys. 37 (1996) 1086-1088 | 10.1063/1.531427 | null | gr-qc | null | We present a counter example to a theorem given by Amir {\em et al.} J. Math.
Phys. {\bf 35}, 3005 (1994). We also comment on a misleading statements of the
same reference.
| [
{
"created": "Tue, 3 Oct 1995 20:59:35 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Oct 1995 22:52:42 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Bertolotti",
"R.",
"",
"University\n of Los Andes, Mèrida, Venezuela"
],
[
"Contreras",
"G.",
"",
"University\n of Los Andes, Mèrida, Venezuela"
],
[
"Núñez",
"L. A.",
"",
"University\n of Los Andes, Mèrida, Venezuela"
],
[
"Percoco",
"U.",
"",
"University\n of Los Andes, Mèrida, Venezuela"
],
[
"Carot",
"J.",
"",
"Universitat de les Illes\n Baleares, Mallorca, España"
]
] | We present a counter example to a theorem given by Amir {\em et al.} J. Math. Phys. {\bf 35}, 3005 (1994). We also comment on a misleading statements of the same reference. |
0710.5619 | Saibal Ray | Sumana Bhadra | Electromagnetic Mass Models in General Theory of Relativity | 100 pages, Ph.D. thesis | null | null | null | gr-qc | null | "Electromagnetic mass" where gravitational mass and other physical quantities
originate from the electromagnetic field alone has a century long distinguished
history. In the introductory chapter we have divided this history into three
broad categories -- classical, quantum mechanical and general relativistic.
Each of the categories has been described at a length to get the detailed
picture of the physical background. Recent developments on Repulsive
Electromagnetic Mass Models are of special interest in this introductory part
of the thesis. In this context we have also stated motivation of our work. In
the subsequent chapters we have presented our results and their physical
significances. It is concluded that the electromagnetic mass models which are
the sources of purely electromagnetic origin ``have not only heuristic flavor
associated with the conjecture of Lorentz but even a physics having
unconventional yet novel features characterizing their own contributions
independent of the rest of the physics".
| [
{
"created": "Tue, 30 Oct 2007 11:55:21 GMT",
"version": "v1"
}
] | 2007-10-31 | [
[
"Bhadra",
"Sumana",
""
]
] | "Electromagnetic mass" where gravitational mass and other physical quantities originate from the electromagnetic field alone has a century long distinguished history. In the introductory chapter we have divided this history into three broad categories -- classical, quantum mechanical and general relativistic. Each of the categories has been described at a length to get the detailed picture of the physical background. Recent developments on Repulsive Electromagnetic Mass Models are of special interest in this introductory part of the thesis. In this context we have also stated motivation of our work. In the subsequent chapters we have presented our results and their physical significances. It is concluded that the electromagnetic mass models which are the sources of purely electromagnetic origin ``have not only heuristic flavor associated with the conjecture of Lorentz but even a physics having unconventional yet novel features characterizing their own contributions independent of the rest of the physics". |
gr-qc/9707060 | Torsten Tok | Gerd Rudolph and Torsten Tok and Igor P. Volobuev | Exact solutions in Einstein-Yang-Mills-Dirac systems | 18 pages, LaTeX 2e | J.Math.Phys. 40 (1999) 5890-5904 | 10.1063/1.533061 | null | gr-qc | null | We present exact solutions in Einstein-Yang-Mills-Dirac theories with gauge
groups SU(2) and SU(4) in Robertson-Walker space-time $R \times S^3 $, which
are symmetric under the action of the group SO(4) of spatial rotations. Our
approach is based on the dimensional reduction method for gauge and
gravitational fields and relates symmetric solutions in EYMD theory to certain
solutions of an effective dynamical system.
We interpret our solutions as cosmological solutions with an oscillating
Yang-Mills field passing between topologically distinct vacua. The explicit
form of the solution for spinor field shows that its energy changes the sign
during the evolution of the Yang-Mills field from one vacuum to the other,
which can be considered as production or annihilation of fermions.
Among the obtained solutions there is also a static sphaleron-like solution,
which is a cosmological analogue of the first Bartnik-McKinnon solution in the
presence of fermions.
| [
{
"created": "Wed, 30 Jul 1997 12:51:04 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Rudolph",
"Gerd",
""
],
[
"Tok",
"Torsten",
""
],
[
"Volobuev",
"Igor P.",
""
]
] | We present exact solutions in Einstein-Yang-Mills-Dirac theories with gauge groups SU(2) and SU(4) in Robertson-Walker space-time $R \times S^3 $, which are symmetric under the action of the group SO(4) of spatial rotations. Our approach is based on the dimensional reduction method for gauge and gravitational fields and relates symmetric solutions in EYMD theory to certain solutions of an effective dynamical system. We interpret our solutions as cosmological solutions with an oscillating Yang-Mills field passing between topologically distinct vacua. The explicit form of the solution for spinor field shows that its energy changes the sign during the evolution of the Yang-Mills field from one vacuum to the other, which can be considered as production or annihilation of fermions. Among the obtained solutions there is also a static sphaleron-like solution, which is a cosmological analogue of the first Bartnik-McKinnon solution in the presence of fermions. |
1207.6370 | Enrico Barausse | Enrico Barausse and Thomas P. Sotiriou | A no-go theorem for slowly rotating black holes in Horava-Lifshitz
gravity | 5 pages, 1 figure. Very minor changes to text (results unchanged) to
match version accepted for publication in Phys. Rev. Lett | Phys. Rev. Lett. 109, 181101 (2012), Erratum Phys. Rev. Lett. 110,
039902(E) (2013) | 10.1103/PhysRevLett.109.181101 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider slowly rotating, stationary, axisymmetric black holes in the
infrared limit of Horava-Lifshitz gravity. We show that such solutions do not
exist, provided that they are regular everywhere apart from the central
singularity. This has profound implications for the viability of the theory,
considering the astrophysical evidence for the existence of black holes with
non-zero spin.
NOTE ADDED: A subtlety in the dynamical equivalence between Horava-Lifshitz
gravity and Einstein-aether theory has been missed and this has seriously
affected the conclusions of this paper. Please see arXiv:1212.1334 for a full
discussion
| [
{
"created": "Thu, 26 Jul 2012 19:03:01 GMT",
"version": "v1"
},
{
"created": "Sat, 29 Sep 2012 20:46:14 GMT",
"version": "v2"
},
{
"created": "Fri, 7 Dec 2012 15:04:56 GMT",
"version": "v3"
}
] | 2013-04-29 | [
[
"Barausse",
"Enrico",
""
],
[
"Sotiriou",
"Thomas P.",
""
]
] | We consider slowly rotating, stationary, axisymmetric black holes in the infrared limit of Horava-Lifshitz gravity. We show that such solutions do not exist, provided that they are regular everywhere apart from the central singularity. This has profound implications for the viability of the theory, considering the astrophysical evidence for the existence of black holes with non-zero spin. NOTE ADDED: A subtlety in the dynamical equivalence between Horava-Lifshitz gravity and Einstein-aether theory has been missed and this has seriously affected the conclusions of this paper. Please see arXiv:1212.1334 for a full discussion |
1110.0813 | Dieter Luest | Dieter Lust, Marios Petropoulos | Comment on superluminality in general relativity | 6 pages | null | 10.1088/0264-9381/29/8/085013 | CPHT-RR066.0911, MPP-2011-115, LMU-ASC 45/11 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General relativity provides an appropriate framework for addressing the issue
of sub- or superluminality as an apparent effect. Even though a massless
particle travels on the light cone, its average velocity over a finite path
measured by different observers is not necessarily equal to the velocity of
light, as a consequence of the time dilation or contraction in gravitational
fields. This phenomenon occurs in either direction (increase or depletion)
irrespectively of the details and strength of the gravitational interaction.
Hence, it does not intrinsically guarantee superluminality, even when the
gravitational field is reinforced.
| [
{
"created": "Tue, 4 Oct 2011 19:25:29 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Lust",
"Dieter",
""
],
[
"Petropoulos",
"Marios",
""
]
] | General relativity provides an appropriate framework for addressing the issue of sub- or superluminality as an apparent effect. Even though a massless particle travels on the light cone, its average velocity over a finite path measured by different observers is not necessarily equal to the velocity of light, as a consequence of the time dilation or contraction in gravitational fields. This phenomenon occurs in either direction (increase or depletion) irrespectively of the details and strength of the gravitational interaction. Hence, it does not intrinsically guarantee superluminality, even when the gravitational field is reinforced. |
1909.09519 | John Barrow | John D. Barrow | Sudden Singularities in Brans-Dicke Cosmology and its Generalisations | 7 pages, no figures | Class. Quantum Grav. 37, 065014 (2020) | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that cosmological sudden singularities that respect the energy
conditions can occur at finite times in Brans-Dicke and more general
scalar-tensor theories of gravity. We construct these explicitly in the
Friedmann universes. Higher-order versions of these singularities are also
possible, including those that arise with when scalar fields have a
self-interaction potential of power-law form.7 pages, no figures
| [
{
"created": "Fri, 20 Sep 2019 14:10:05 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Jan 2020 12:00:30 GMT",
"version": "v2"
}
] | 2020-02-21 | [
[
"Barrow",
"John D.",
""
]
] | We show that cosmological sudden singularities that respect the energy conditions can occur at finite times in Brans-Dicke and more general scalar-tensor theories of gravity. We construct these explicitly in the Friedmann universes. Higher-order versions of these singularities are also possible, including those that arise with when scalar fields have a self-interaction potential of power-law form.7 pages, no figures |
2111.14214 | Lucrezia Ravera | Damianos Iosifidis, Ratbay Myrzakulov, Lucrezia Ravera, Gulmira
Yergaliyeva, Koblandy Yerzhanov | Metric-Affine Vector-Tensor Correspondence and Implications in
$F(R,T,Q,\mathcal{T},\mathcal{D})$ gravity | 28 pages | Phys. Dark Univ. 37 (2022), 101094 | 10.1016/j.dark.2022.101094 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend the results of antecedent literature on quadratic Metric-Affine
Gravity by studying a new quadratic gravity action in vacuum which, besides the
usual (non-Riemannian) Einstein-Hilbert contribution, involves all the parity
even quadratic terms in torsion and non-metricity plus a Lagrangian that is
quadratic in the field-strengths of the torsion and non-metricity vector
traces. The theory result to be equivalent, on-shell, to a Vector-Tensor
theory. We also discuss the sub-cases in which the contribution to the
Lagrangian quadratic in the field-strengths of the torsion and non-metricity
vectors just exhibits one of the aforementioned quadratic terms. We then report
on implications of our findings in the context of
$F(R,T,Q,\mathcal{T},\mathcal{D})$ gravity.
| [
{
"created": "Sun, 28 Nov 2021 19:11:56 GMT",
"version": "v1"
}
] | 2022-12-26 | [
[
"Iosifidis",
"Damianos",
""
],
[
"Myrzakulov",
"Ratbay",
""
],
[
"Ravera",
"Lucrezia",
""
],
[
"Yergaliyeva",
"Gulmira",
""
],
[
"Yerzhanov",
"Koblandy",
""
]
] | We extend the results of antecedent literature on quadratic Metric-Affine Gravity by studying a new quadratic gravity action in vacuum which, besides the usual (non-Riemannian) Einstein-Hilbert contribution, involves all the parity even quadratic terms in torsion and non-metricity plus a Lagrangian that is quadratic in the field-strengths of the torsion and non-metricity vector traces. The theory result to be equivalent, on-shell, to a Vector-Tensor theory. We also discuss the sub-cases in which the contribution to the Lagrangian quadratic in the field-strengths of the torsion and non-metricity vectors just exhibits one of the aforementioned quadratic terms. We then report on implications of our findings in the context of $F(R,T,Q,\mathcal{T},\mathcal{D})$ gravity. |
2407.20688 | Marco Schreck MS | Jo\~ao Victor V. Santos and Marco Schreck | Hamiltonian formulation for scalar model of spontaneous spacetime
symmetry violation in gravity | 48 pages, 2 figures, 2 tables | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The focus of this article is on a modification of General Relativity (GR)
governed by a dynamical scalar field. The latter is able to acquire a nonzero
spacetime-dependent vacuum expectation value, which gives rise to a spontaneous
violation of spacetime symmetries. Based on the (3+1) decomposition, we
demonstrate how to develop the Hamiltonian formulation for this model. Having
done so, our primary interest is to understand how spontaneous spacetime
symmetry violation manifests itself in such a setting. In particular, we find
that the constraint structure of GR is preserved, although the constraints are
clearly modified by the scalar background field. These results emphasize the
beauty of spontaneous spacetime symmetry violation in gravity from the
viewpoint of the Hamiltonian formulation. They may pose the base for further
studies of more sophisticated models of vector and higher-rank tensor fields.
Moreover, the description developed can bear fruits when applied within
phenomenological quests for spacetime symmetry violation in gravity, in
particular, at cosmological scales.
| [
{
"created": "Tue, 30 Jul 2024 09:29:36 GMT",
"version": "v1"
}
] | 2024-07-31 | [
[
"Santos",
"João Victor V.",
""
],
[
"Schreck",
"Marco",
""
]
] | The focus of this article is on a modification of General Relativity (GR) governed by a dynamical scalar field. The latter is able to acquire a nonzero spacetime-dependent vacuum expectation value, which gives rise to a spontaneous violation of spacetime symmetries. Based on the (3+1) decomposition, we demonstrate how to develop the Hamiltonian formulation for this model. Having done so, our primary interest is to understand how spontaneous spacetime symmetry violation manifests itself in such a setting. In particular, we find that the constraint structure of GR is preserved, although the constraints are clearly modified by the scalar background field. These results emphasize the beauty of spontaneous spacetime symmetry violation in gravity from the viewpoint of the Hamiltonian formulation. They may pose the base for further studies of more sophisticated models of vector and higher-rank tensor fields. Moreover, the description developed can bear fruits when applied within phenomenological quests for spacetime symmetry violation in gravity, in particular, at cosmological scales. |
1011.0557 | Farhad Darabi | F. Darabi and S. Jalalzadeh | One-loop quantum cosmological correction to the gravitational constant
using the kink solution in de Sitter universe | 18 pages | Mod.Phys.Lett.A25:2955-2971,2010 | 10.1142/S0217732310033943 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we show the equivalence between a classical static scalar
field theory and the (closed) de Sitter cosmological model whose potential
represents shape invariance property. Based on this equivalence, we calculate
the one-loop quantum cosmological correction to the ground state energy of the
kink-like solution in the (closed) de Sitter cosmological model in which the
fluctuation potential $V^{\prime\prime}$ has a shape invariance property. It is
shown that this type of correction, which yields a renormalized mass in the
case of scalar field theory, may be {\it interpreted} as a renormalized
gravitational constant in the case of (closed) de Sitter cosmological model.
Keywords: One-loop correction; kink energy; shape invariance; zeta function
regularization; de Sitter universe.
| [
{
"created": "Tue, 2 Nov 2010 09:58:01 GMT",
"version": "v1"
}
] | 2011-06-06 | [
[
"Darabi",
"F.",
""
],
[
"Jalalzadeh",
"S.",
""
]
] | In this paper, we show the equivalence between a classical static scalar field theory and the (closed) de Sitter cosmological model whose potential represents shape invariance property. Based on this equivalence, we calculate the one-loop quantum cosmological correction to the ground state energy of the kink-like solution in the (closed) de Sitter cosmological model in which the fluctuation potential $V^{\prime\prime}$ has a shape invariance property. It is shown that this type of correction, which yields a renormalized mass in the case of scalar field theory, may be {\it interpreted} as a renormalized gravitational constant in the case of (closed) de Sitter cosmological model. Keywords: One-loop correction; kink energy; shape invariance; zeta function regularization; de Sitter universe. |
1508.07507 | Stanley P. Gudder | Stan Gudder | Wave Equations for Discrete Quantum Gravity | 17 pages, no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article is based on the covariant causal set ($c$-causet) approach to
discrete quantum gravity. A $c$-causet $x$ is a finite partially ordered set
that has a unique labeling of its vertices. A rate of change on $x$ is
described by a covariant difference operator and this operator acting on a wave
function forms the left side of the wave equation. The right side is given by
an energy term acting on the wave function. Solutions to the wave equation
corresponding to certain pairs of paths in $x$ are added and normalized to form
a unique state. The modulus squared of the state gives probabilities that a
pair of interacting particles is at various locations given by pairs of
vertices in $x$. We illustrate this model for a few of the simplest nontrivial
examples of $c$-causets. Three forces are considered, the attractive and
repulsive electric forces and the strong nuclear force. Large models get much
more complicated and will probably require a computer to analyze.
| [
{
"created": "Sat, 29 Aug 2015 21:48:17 GMT",
"version": "v1"
}
] | 2015-09-01 | [
[
"Gudder",
"Stan",
""
]
] | This article is based on the covariant causal set ($c$-causet) approach to discrete quantum gravity. A $c$-causet $x$ is a finite partially ordered set that has a unique labeling of its vertices. A rate of change on $x$ is described by a covariant difference operator and this operator acting on a wave function forms the left side of the wave equation. The right side is given by an energy term acting on the wave function. Solutions to the wave equation corresponding to certain pairs of paths in $x$ are added and normalized to form a unique state. The modulus squared of the state gives probabilities that a pair of interacting particles is at various locations given by pairs of vertices in $x$. We illustrate this model for a few of the simplest nontrivial examples of $c$-causets. Three forces are considered, the attractive and repulsive electric forces and the strong nuclear force. Large models get much more complicated and will probably require a computer to analyze. |
gr-qc/9310007 | Harald H. Soleng | H. H. Soleng | Inverse Square Law of Gravitation in (2+1)-Dimensional Space-Time as a
Consequence of Casimir Energy | 10 pages, LaTeX, Report: UPR-0540-T, To appear in Physica Scripta | Phys.Scripta 48:649-652,1993 | 10.1088/0031-8949/48/6/002 | null | gr-qc | null | The gravitational effect of vacuum polarization in space exterior to a
particle in (2+1)-dimensional Einstein theory is investigated. In the weak
field limit this gravitational field corresponds to an inverse square law of
gravitational attraction, even though the gravitational mass of the quantum
vacuum is negative. The paradox is resolved by considering a particle of finite
extension and taking into account the vacuum polarization in its interior.
| [
{
"created": "Mon, 4 Oct 1993 12:18:04 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Soleng",
"H. H.",
""
]
] | The gravitational effect of vacuum polarization in space exterior to a particle in (2+1)-dimensional Einstein theory is investigated. In the weak field limit this gravitational field corresponds to an inverse square law of gravitational attraction, even though the gravitational mass of the quantum vacuum is negative. The paradox is resolved by considering a particle of finite extension and taking into account the vacuum polarization in its interior. |
2407.11860 | Adam S. Wilkinson | Adam S. Wilkinson, Jorma Louko | Local quantum detection of cosmological expansion: Unruh-DeWitt in
spatially compact Milne | 17 pages, 7 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyse the excitations and de-excitations of an inertial Unruh-DeWitt
detector in the $(1+1)$-dimensional expanding Milne cosmology with compact
spatial sections, coupled to a real massless scalar field with either untwisted
or twisted boundary conditions, prepared in the conformal vacuum. We find the
detector's response as a function of the energy gap, the Milne spatial
circumference parameter, the interaction duration, the age of the universe at
the switch-on moment, the detector's peculiar velocity at the switch-on moment,
and, for the untwisted field, the state of the zero mode. Asymptotic analytic
results are obtained at large energy gap and at large circumference parameter,
in each case recovering the Minkowski vacuum response in the leading order, and
in the double limit of small circumference parameter and late cosmological
time, recovering the response in a static Minkowski cylinder. Numerical results
are given in the interpolating regimes. The results confirm the detector's
sensitivity to both classical and quantum properties of its environment.
| [
{
"created": "Tue, 16 Jul 2024 15:47:35 GMT",
"version": "v1"
}
] | 2024-07-17 | [
[
"Wilkinson",
"Adam S.",
""
],
[
"Louko",
"Jorma",
""
]
] | We analyse the excitations and de-excitations of an inertial Unruh-DeWitt detector in the $(1+1)$-dimensional expanding Milne cosmology with compact spatial sections, coupled to a real massless scalar field with either untwisted or twisted boundary conditions, prepared in the conformal vacuum. We find the detector's response as a function of the energy gap, the Milne spatial circumference parameter, the interaction duration, the age of the universe at the switch-on moment, the detector's peculiar velocity at the switch-on moment, and, for the untwisted field, the state of the zero mode. Asymptotic analytic results are obtained at large energy gap and at large circumference parameter, in each case recovering the Minkowski vacuum response in the leading order, and in the double limit of small circumference parameter and late cosmological time, recovering the response in a static Minkowski cylinder. Numerical results are given in the interpolating regimes. The results confirm the detector's sensitivity to both classical and quantum properties of its environment. |
0710.2915 | Lior M. Burko | Carl J. Blaksley and Lior M. Burko | The late-time tails in the Reissner-Nordstr\"{o}m spacetime revisited | 11 pages, 13 figues, 1 table. Submitted to Phys. Rev. D | Phys.Rev.D76:104035,2007 | 10.1103/PhysRevD.76.104035 | null | gr-qc | null | We propose that the late-time tail problem in the Reissner-Nordstr\"{o}m (RN)
spacetime is dual to a tail problem in the Schwarzschild spacetime with a
different initial data set: at a fixed observation point the asymptotic decay
rate of the fields are equal. This duality is used to find the decay rate for
tails in RN. This decay rate is exactly as in Schwarzschild, including the case
of the extremely-charged RN spacetime (ERN). The only case where any deviation
from the Schwarzschild decay rate is found is the case of the tails along the
event horizon of an ERN spacetime, where the decay rate is the same as at
future null infinity. As observed at a fixed location, the decay rate in ERN is
the same as in Schwarzschild. We verify these expectations with numerical
simulations.
| [
{
"created": "Mon, 15 Oct 2007 21:11:54 GMT",
"version": "v1"
}
] | 2014-01-14 | [
[
"Blaksley",
"Carl J.",
""
],
[
"Burko",
"Lior M.",
""
]
] | We propose that the late-time tail problem in the Reissner-Nordstr\"{o}m (RN) spacetime is dual to a tail problem in the Schwarzschild spacetime with a different initial data set: at a fixed observation point the asymptotic decay rate of the fields are equal. This duality is used to find the decay rate for tails in RN. This decay rate is exactly as in Schwarzschild, including the case of the extremely-charged RN spacetime (ERN). The only case where any deviation from the Schwarzschild decay rate is found is the case of the tails along the event horizon of an ERN spacetime, where the decay rate is the same as at future null infinity. As observed at a fixed location, the decay rate in ERN is the same as in Schwarzschild. We verify these expectations with numerical simulations. |
1512.01352 | David Vocke | Francesco Marino, Calum Maitland, David Vocke, Antonello Ortolan,
Daniele Faccio | Emergent geometries and nonlinear-wave dynamics in photon fluids | null | null | null | null | gr-qc physics.flu-dyn physics.optics | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Nonlinear waves in defocusing media are investigated in the framework of the
hydrodynamic description of light as a photon fluid. The observations are
interpreted in terms of an emergent curved spacetime generated by the waves
themselves, which fully determines their dynamics. The spacetime geometry
emerges naturally as a result of the nonlinear interaction between the waves
and the self-induced background flow. In particular, as observed in real
fluids, different points of the wave profile propagate at different velocities
leading to the self-steepening of the wave front and to the formation of a
shock. This phenomenon can be associated to a curvature singularity of the
emergent metric. Our analysis offers an alternative insight into the problem of
shock formation and provides a demonstration of an analogue gravity model that
goes beyond the kinematic level.
| [
{
"created": "Fri, 4 Dec 2015 09:45:48 GMT",
"version": "v1"
}
] | 2015-12-07 | [
[
"Marino",
"Francesco",
""
],
[
"Maitland",
"Calum",
""
],
[
"Vocke",
"David",
""
],
[
"Ortolan",
"Antonello",
""
],
[
"Faccio",
"Daniele",
""
]
] | Nonlinear waves in defocusing media are investigated in the framework of the hydrodynamic description of light as a photon fluid. The observations are interpreted in terms of an emergent curved spacetime generated by the waves themselves, which fully determines their dynamics. The spacetime geometry emerges naturally as a result of the nonlinear interaction between the waves and the self-induced background flow. In particular, as observed in real fluids, different points of the wave profile propagate at different velocities leading to the self-steepening of the wave front and to the formation of a shock. This phenomenon can be associated to a curvature singularity of the emergent metric. Our analysis offers an alternative insight into the problem of shock formation and provides a demonstration of an analogue gravity model that goes beyond the kinematic level. |
1912.04275 | S. Danial Forghani | S. Danial Forghani, S. Habib Mazharimousavi, and Mustafa Halilsoy | Thin-Shell Wormhole Satisfying Energy Conditions | 5 pages, 1 figure (including 6 subfigures) | null | 10.1016/j.physletb.2020.135374 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The quartic self-interacting conformal scalar field is used to construct a
thin-shell wormhole satisfying all energy conditions. Accompanying the scalar
field is the extremal Reissner-Nordstr\"om black hole with a positive
cosmological constant. New junction conditions apt for the higher-order terms
are introduced in the Gaussian normal coordinates. Our approach may provide a
guideline towards getting rid of exotic matter in TSWs.
| [
{
"created": "Sun, 8 Dec 2019 08:31:47 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Feb 2020 14:42:04 GMT",
"version": "v2"
}
] | 2020-03-31 | [
[
"Forghani",
"S. Danial",
""
],
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Halilsoy",
"Mustafa",
""
]
] | The quartic self-interacting conformal scalar field is used to construct a thin-shell wormhole satisfying all energy conditions. Accompanying the scalar field is the extremal Reissner-Nordstr\"om black hole with a positive cosmological constant. New junction conditions apt for the higher-order terms are introduced in the Gaussian normal coordinates. Our approach may provide a guideline towards getting rid of exotic matter in TSWs. |
1308.1076 | Alcides Garat | Alcides Garat | The equivalence between local inertial frames and electromagnetic gauge
in Einstein-Maxwell theories | 10 pages. arXiv admin note: substantial text overlap with
arXiv:1306.2174, arXiv:1306.0602, arXiv:1306.5784, arXiv:1306.4005 | International Journal of Geometric Methods in Modern Physics Vol.
21, No. 03, 2450056 (2024) | 10.1142/S0219887824500567 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We are going to prove that locally the inertial frames and gauge states of
the electromagnetic field are equivalent. This proof will be valid for
Einstein-Maxwell theories in four-dimensional Lorentzian spacetimes. Use will
be made of theorems proved in a previous manuscript. These theorems state that
locally the group of electromagnetic gauge transformations is isomorphic to the
local Lorentz transformations of a special set of tetrad vectors. The tetrad
that locally and covariantly diagonalizes any non-null electromagnetic
stress-energy tensor. Two isomorphisms, one for each plane defined locally by
two separate sets of two vectors each. In particular, we are going to use the
plane defined by the timelike and one spacelike vector, plane or blade one.
These results will be extended to any tetrad that results in a local Lorentz
transformation of the special tetrad that locally and covariantly diagonalizes
the stress-energy tensor.
| [
{
"created": "Mon, 5 Aug 2013 19:17:24 GMT",
"version": "v1"
}
] | 2024-07-16 | [
[
"Garat",
"Alcides",
""
]
] | We are going to prove that locally the inertial frames and gauge states of the electromagnetic field are equivalent. This proof will be valid for Einstein-Maxwell theories in four-dimensional Lorentzian spacetimes. Use will be made of theorems proved in a previous manuscript. These theorems state that locally the group of electromagnetic gauge transformations is isomorphic to the local Lorentz transformations of a special set of tetrad vectors. The tetrad that locally and covariantly diagonalizes any non-null electromagnetic stress-energy tensor. Two isomorphisms, one for each plane defined locally by two separate sets of two vectors each. In particular, we are going to use the plane defined by the timelike and one spacelike vector, plane or blade one. These results will be extended to any tetrad that results in a local Lorentz transformation of the special tetrad that locally and covariantly diagonalizes the stress-energy tensor. |
0808.1339 | Ignazio Licata | Ignazio Licata, Leonardo Chiatti | The Archaic Universe: Big Bang, Cosmological Term and the Quantum Origin
of Time in Projective Cosmology | 17 pgs | Int.J.Theor.Phys.48:1003-1018,2009 | 10.1007/s10773-008-9874-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article proposes some cosmological reflections at the qualitative and
conjectural level, suggested by the Fantappie & Arcidiacono projective
relativity theory. The difference will firstly be discussed between two types
of singularity in this theory: geometric (de Sitter horizon) and physical (big
bang, big crunch). The reasons for the existence of geometric singularities are
deeply rooted in the principle of inertia and in the principle of relativity,
while physical singularities are associated with the creation or destruction of
matter. In this framework, quantum mechanics is introduced through a particular
interpretation of Bohm holomovement. Finally, a possible mechanism is discussed
for the genesis of the cosmological term. No form of inflation appears in the
scenario described.
| [
{
"created": "Sat, 9 Aug 2008 08:39:58 GMT",
"version": "v1"
}
] | 2009-03-24 | [
[
"Licata",
"Ignazio",
""
],
[
"Chiatti",
"Leonardo",
""
]
] | This article proposes some cosmological reflections at the qualitative and conjectural level, suggested by the Fantappie & Arcidiacono projective relativity theory. The difference will firstly be discussed between two types of singularity in this theory: geometric (de Sitter horizon) and physical (big bang, big crunch). The reasons for the existence of geometric singularities are deeply rooted in the principle of inertia and in the principle of relativity, while physical singularities are associated with the creation or destruction of matter. In this framework, quantum mechanics is introduced through a particular interpretation of Bohm holomovement. Finally, a possible mechanism is discussed for the genesis of the cosmological term. No form of inflation appears in the scenario described. |
1611.07854 | Francisco Fabi\'an Gonz\'alez | Francisco Fabi\'an Gonz\'alez, Tomislav Prokopec | Renormalization group approach to scalar quantum electrodynamics on de
Sitter | 12 pages, 16 figures | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the quantum loop effects in scalar electrodynamics on de Sitter
space by making use of the functional renormalization group approach. We first
integrate out the photon field, which can be done exactly to leading (zeroth)
order in the gradients of the scalar field, thereby making this method suitable
for investigating the dynamics of the infrared sector of the theory. Assuming
that the scalar remains light we then apply the functional renormalization
group methods to the resulting effective scalar theory and focus on
investigating the effective potential, which is the leading order contribution
in the gradient expansion of the effective action. We find symmetry restoration
at a critical renormalization scale $\kappa=\kappa_{\rm cr}$ much below the
Hubble scale $H$. When compared with the results of Serreau and Guilleux
[arXiv:1306.3846 [hep-th], arXiv:1506.06183 [hep-th]] we find that the photon
facilitates symmetry restoration such that it occurs at an RG scale
$\kappa_{\rm cr}$ that is higher than in the case of a pure scalar theory. The
true effective potential is recovered when $\kappa\rightarrow 0$ and in that
limit one obtains the results that agree with those of stochastic inflation,
provided one interprets it in the sense as advocated by Lazzari and Prokopec
[arXiv:1304.0404 [hep-th]].
| [
{
"created": "Wed, 23 Nov 2016 16:11:14 GMT",
"version": "v1"
}
] | 2016-11-24 | [
[
"González",
"Francisco Fabián",
""
],
[
"Prokopec",
"Tomislav",
""
]
] | We consider the quantum loop effects in scalar electrodynamics on de Sitter space by making use of the functional renormalization group approach. We first integrate out the photon field, which can be done exactly to leading (zeroth) order in the gradients of the scalar field, thereby making this method suitable for investigating the dynamics of the infrared sector of the theory. Assuming that the scalar remains light we then apply the functional renormalization group methods to the resulting effective scalar theory and focus on investigating the effective potential, which is the leading order contribution in the gradient expansion of the effective action. We find symmetry restoration at a critical renormalization scale $\kappa=\kappa_{\rm cr}$ much below the Hubble scale $H$. When compared with the results of Serreau and Guilleux [arXiv:1306.3846 [hep-th], arXiv:1506.06183 [hep-th]] we find that the photon facilitates symmetry restoration such that it occurs at an RG scale $\kappa_{\rm cr}$ that is higher than in the case of a pure scalar theory. The true effective potential is recovered when $\kappa\rightarrow 0$ and in that limit one obtains the results that agree with those of stochastic inflation, provided one interprets it in the sense as advocated by Lazzari and Prokopec [arXiv:1304.0404 [hep-th]]. |
2008.07446 | Branislav Nikolic | Branislav Nikolic | Quantum Geometrodynamics of Higher Derivative Theories with and without
Conformal Symmetry | Doctoral dissertation (University of Cologne), 273 pages, Identical
to the final published version except for minor formatting improvements and
corrected typos | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main goal of this thesis is to quantize the Einstein-Hilbert action
extended by the quadratic curvature terms within the canonical quantization
approach, thus formulating quantum geometrodynamics of the higher derivative
theories. The motivation is to provide an alternative to the standard canonical
quantization based on the Einstein-Hilbert action alone, because the latter
does not generate the quadratic curvature terms in the semiclassical limit. A
particular formulation of a semiclassical approximation scheme is employed
which ensures that the effects of the quadratic curvature terms become
perturbative in the semiclassical limit. This leaves the classical General
Relativity intact, while naturally giving rise to its first semiclassical
corrections. Another topic of interest is a classical theory where the
quadratic Ricci scalar and the Einstein-Hilbert term are absent from the
action, which then enjoys the symmetry with respect to the conformal
transformation of fields (local Weyl rescaling). We pay a special attention to
this case, since it provides a natural setting for the absence of the notion of
a physical length scale. Certain useful model-independent tools are also
constructed in this thesis. Firstly, dimensionless coordinates and the
unimodular decomposition of the metric are used to expose the only conformally
variant degree of freedom, making the geometrical origin of the physical length
scale apparent. With such an approach several earlier results become much more
transparent. Secondly, using unimodular-conformal variables a model-independent
generator of conformal field transformations is constructed in terms of which a
reformulation of the definition of conformal invariance is given. Thirdly, it
is argued that a canonical quantization scheme makes more sense to be based on
the quantization of generators of relevant transformations, than on first class
constraints.
| [
{
"created": "Mon, 17 Aug 2020 16:07:29 GMT",
"version": "v1"
}
] | 2020-08-18 | [
[
"Nikolic",
"Branislav",
""
]
] | The main goal of this thesis is to quantize the Einstein-Hilbert action extended by the quadratic curvature terms within the canonical quantization approach, thus formulating quantum geometrodynamics of the higher derivative theories. The motivation is to provide an alternative to the standard canonical quantization based on the Einstein-Hilbert action alone, because the latter does not generate the quadratic curvature terms in the semiclassical limit. A particular formulation of a semiclassical approximation scheme is employed which ensures that the effects of the quadratic curvature terms become perturbative in the semiclassical limit. This leaves the classical General Relativity intact, while naturally giving rise to its first semiclassical corrections. Another topic of interest is a classical theory where the quadratic Ricci scalar and the Einstein-Hilbert term are absent from the action, which then enjoys the symmetry with respect to the conformal transformation of fields (local Weyl rescaling). We pay a special attention to this case, since it provides a natural setting for the absence of the notion of a physical length scale. Certain useful model-independent tools are also constructed in this thesis. Firstly, dimensionless coordinates and the unimodular decomposition of the metric are used to expose the only conformally variant degree of freedom, making the geometrical origin of the physical length scale apparent. With such an approach several earlier results become much more transparent. Secondly, using unimodular-conformal variables a model-independent generator of conformal field transformations is constructed in terms of which a reformulation of the definition of conformal invariance is given. Thirdly, it is argued that a canonical quantization scheme makes more sense to be based on the quantization of generators of relevant transformations, than on first class constraints. |
gr-qc/0605091 | Karel Van Acoleyen | I. Navarro and K. Van Acoleyen | Long distance modifications of gravity in four dimensions | 4 pages, contribution to the proceedings of the Rencontres de
Moriond: Contents and Structures of the Universe, March 18-25, 2006, La
Thuile | null | null | DAMTP-2006-41, DCPT/06/62, IPPP/06/31 | gr-qc | null | We discuss some general characteristics of modifications of the 4D
Einstein-Hilbert action that become important for low space-time curvatures. In
particular we focus on the chameleon-like behaviour of the massive
gravitational degrees of freedom. Generically there is at least one extra
scalar that is light on cosmic scales, but for certain models it becomes heavy
close to any mass source.
| [
{
"created": "Tue, 16 May 2006 19:48:31 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Navarro",
"I.",
""
],
[
"Van Acoleyen",
"K.",
""
]
] | We discuss some general characteristics of modifications of the 4D Einstein-Hilbert action that become important for low space-time curvatures. In particular we focus on the chameleon-like behaviour of the massive gravitational degrees of freedom. Generically there is at least one extra scalar that is light on cosmic scales, but for certain models it becomes heavy close to any mass source. |
1508.01810 | Istvan Racz | Istv\'an R\'acz | Constraints as evolutionary systems | 18 pages; exposition improved concerning the algebraic hyperbolic
system; references added; to appear in CQG | Class. Quantum Grav. 33 015014 (2016) | 10.1088/0264-9381/33/1/015014 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The constraint equations for smooth $[n+1]$-dimensional (with $n\geq 3$)
Riemannian or Lorentzian spaces satisfying the Einstein field equations are
considered. It is shown, regardless of the signature of the primary space, that
the constraints can be put into the form of an evolutionary system comprised
either by a first order symmetric hyperbolic system and a parabolic equation
or, alternatively, by a symmetrizable hyperbolic system and a subsidiary
algebraic relation. In both cases the (local) existence and uniqueness of
solutions are also discussed.
| [
{
"created": "Fri, 7 Aug 2015 20:39:04 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Sep 2015 21:12:31 GMT",
"version": "v2"
},
{
"created": "Fri, 4 Dec 2015 11:20:38 GMT",
"version": "v3"
}
] | 2015-12-15 | [
[
"Rácz",
"István",
""
]
] | The constraint equations for smooth $[n+1]$-dimensional (with $n\geq 3$) Riemannian or Lorentzian spaces satisfying the Einstein field equations are considered. It is shown, regardless of the signature of the primary space, that the constraints can be put into the form of an evolutionary system comprised either by a first order symmetric hyperbolic system and a parabolic equation or, alternatively, by a symmetrizable hyperbolic system and a subsidiary algebraic relation. In both cases the (local) existence and uniqueness of solutions are also discussed. |
0711.0090 | Kirill Krasnov | Kirill Krasnov | On deformations of Ashtekar's constraint algebra | 3 pages, no figures | Phys.Rev.Lett.100:081102,2008 | 10.1103/PhysRevLett.100.081102 | null | gr-qc astro-ph hep-th | null | We show that the constraint algebra of Ashtekar's Hamiltonian formulation of
general relativity can be non-trivially deformed by allowing the cosmological
constant to become an arbitrary function of the (Weyl) curvature. Our result
implies that there is not one but infinitely many (parameterized by an
arbitrary function) four-dimensional gravity theories propagating two degrees
of freedom.
| [
{
"created": "Thu, 1 Nov 2007 09:20:27 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Krasnov",
"Kirill",
""
]
] | We show that the constraint algebra of Ashtekar's Hamiltonian formulation of general relativity can be non-trivially deformed by allowing the cosmological constant to become an arbitrary function of the (Weyl) curvature. Our result implies that there is not one but infinitely many (parameterized by an arbitrary function) four-dimensional gravity theories propagating two degrees of freedom. |
gr-qc/0211034 | Alexander A. Chernitskii | Alexander A. Chernitskii | Induced gravitation as nonlinear electrodynamics effect | 4 pages, talk given at the V International Conference on
COSMOPARTICLE PHYSICS (Cosmion-2001) Dedicated to 80-th Anniversary of Andrei
D. Sakharov (21-30 May 2001, Moscow-St.Petersburg, Russia) | Grav.Cosmol.Suppl.8N1:157-160,2002 | null | null | gr-qc | null | The effect of induced Riemann geometry in nonlinear electrodynamics is
considered. The possibility for description of real gravitation by this effect
is discussed.
| [
{
"created": "Mon, 11 Nov 2002 11:24:13 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Chernitskii",
"Alexander A.",
""
]
] | The effect of induced Riemann geometry in nonlinear electrodynamics is considered. The possibility for description of real gravitation by this effect is discussed. |
1807.00890 | Serguei Krasnikov | S. Krasnikov | Schwarzschild-Like Wormholes as Accelerators | A few corrections, and clarifications. 2 graphs are added | Phys. Rev. D 98, 104048 (2018) | 10.1103/PhysRevD.98.104048 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a stationary spacetime $S$ consider a pair of free falling particles that
collide with the energy $E_{\rm c.m.}$ (as measured in the center-of-mass
system). Let the metric of $S$ or/and the trajectories of the particles depend
on a parameter $ k$. Then $S$ is said to be a "(super) accelerator" if $E_{\rm
c.m.}$ grows unboundedly with $ k$, even though the energies of the particles
at infinity remain bounded. The existence of naturally occurring super
accelerators would make it possible to observe otherwise inaccessible
phenomena. This is why in recent years a lot of spacetimes were tested on being
super accelerators.
In this paper a wormhole $W$ of an especially simple---and hence, hopefully,
realistic---geometry is considered: it is static, spherically symmetric, its
matter source is confined to a compact neighbourhood of the throat, and the
$tt$-component (in the Schwarzschild coordinates) of its metric has a single
minimum. It is shown that such a wormhole is a super accelerator with $ k\equiv
\frac 13\ln |g_{tt\ \mathrm{min}}|$. In contrast to the rotating Teo wormhole,
considered by Tsukamoto and Bambi, $W$ cannot accelerate the collision products
on their way to a distant observer. On the other hand, in contrast to the black
hole colliders, $W$ does not need such acceleration to make those products
detectable.
| [
{
"created": "Mon, 2 Jul 2018 21:11:34 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Nov 2018 18:41:18 GMT",
"version": "v2"
}
] | 2018-12-05 | [
[
"Krasnikov",
"S.",
""
]
] | In a stationary spacetime $S$ consider a pair of free falling particles that collide with the energy $E_{\rm c.m.}$ (as measured in the center-of-mass system). Let the metric of $S$ or/and the trajectories of the particles depend on a parameter $ k$. Then $S$ is said to be a "(super) accelerator" if $E_{\rm c.m.}$ grows unboundedly with $ k$, even though the energies of the particles at infinity remain bounded. The existence of naturally occurring super accelerators would make it possible to observe otherwise inaccessible phenomena. This is why in recent years a lot of spacetimes were tested on being super accelerators. In this paper a wormhole $W$ of an especially simple---and hence, hopefully, realistic---geometry is considered: it is static, spherically symmetric, its matter source is confined to a compact neighbourhood of the throat, and the $tt$-component (in the Schwarzschild coordinates) of its metric has a single minimum. It is shown that such a wormhole is a super accelerator with $ k\equiv \frac 13\ln |g_{tt\ \mathrm{min}}|$. In contrast to the rotating Teo wormhole, considered by Tsukamoto and Bambi, $W$ cannot accelerate the collision products on their way to a distant observer. On the other hand, in contrast to the black hole colliders, $W$ does not need such acceleration to make those products detectable. |
1502.04320 | Daniel Coumbe | D.N. Coumbe | Hypothesis on the Nature of Time | 15 pages, 4 figures. Conforms with version to be published in PRD.
Clarifications and references added | null | 10.1103/PhysRevD.91.124040 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present numerical evidence that fictitious diffusing particles in the
causal dynamical triangulation (CDT) approach to quantum gravity exceed the
speed of light on small distance scales. We argue this superluminal behaviour
is responsible for the appearance of dimensional reduction in the spectral
dimension. By axiomatically enforcing a scale invariant speed of light we show
that time must dilate as a function of relative scale, just as it does as a
function of relative velocity. By calculating the Hausdorff dimension of CDT
diffusion paths we present a seemingly equivalent dual description in terms of
a scale dependent Wick rotation of the metric. Such a modification to the
nature of time may also have relevance for other approaches to quantum gravity.
| [
{
"created": "Sun, 15 Feb 2015 15:05:30 GMT",
"version": "v1"
},
{
"created": "Fri, 1 May 2015 16:30:23 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Jun 2015 09:20:06 GMT",
"version": "v3"
}
] | 2015-09-14 | [
[
"Coumbe",
"D. N.",
""
]
] | We present numerical evidence that fictitious diffusing particles in the causal dynamical triangulation (CDT) approach to quantum gravity exceed the speed of light on small distance scales. We argue this superluminal behaviour is responsible for the appearance of dimensional reduction in the spectral dimension. By axiomatically enforcing a scale invariant speed of light we show that time must dilate as a function of relative scale, just as it does as a function of relative velocity. By calculating the Hausdorff dimension of CDT diffusion paths we present a seemingly equivalent dual description in terms of a scale dependent Wick rotation of the metric. Such a modification to the nature of time may also have relevance for other approaches to quantum gravity. |
2302.02938 | Roberto Maluf | F. M. Belchior, A. R. P. Moreira, R. V. Maluf and C. A. S. Almeida | Localization of abelian gauge fields with Stueckelberg-like geometrical
coupling on $f(T,B)$-thick brane | 28 pages, 7 captioned figures, references added, Enhanced version to
appear in European Physical Journal C | Eur. Phys. J. C 83, 388 (2023) | 10.1140/epjc/s10052-023-11567-y | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In the context of $f(T,B)$ modified teleparallel gravity, we investigate the
influence of torsion scalar $T$ and boundary term $B$ on the confinement of
both the gauge vector and Kalb-Ramond fields. Both fields require a suitable
coupling in five-dimensional braneworld scenarios to yield a normalizable zero
mode. We propose a Stueckelberg-like geometrical coupling that non-minimally
couples the fields to the torsion scalar and boundary term. To set up our
braneworld models, we use the first-order formalism in which two kinds of
superpotential are taken: sine-Gordon and $\phi^{4}$-deformed. The geometrical
coupling is used to produce a localized zero mode. Moreover, we analyze the
massive spectrum for both fields and obtain possible resonant massive modes.
Furthermore, we do not find tachyonic modes leading to a consistent thick
brane.
| [
{
"created": "Mon, 6 Feb 2023 17:12:15 GMT",
"version": "v1"
},
{
"created": "Tue, 2 May 2023 06:49:20 GMT",
"version": "v2"
}
] | 2023-05-12 | [
[
"Belchior",
"F. M.",
""
],
[
"Moreira",
"A. R. P.",
""
],
[
"Maluf",
"R. V.",
""
],
[
"Almeida",
"C. A. S.",
""
]
] | In the context of $f(T,B)$ modified teleparallel gravity, we investigate the influence of torsion scalar $T$ and boundary term $B$ on the confinement of both the gauge vector and Kalb-Ramond fields. Both fields require a suitable coupling in five-dimensional braneworld scenarios to yield a normalizable zero mode. We propose a Stueckelberg-like geometrical coupling that non-minimally couples the fields to the torsion scalar and boundary term. To set up our braneworld models, we use the first-order formalism in which two kinds of superpotential are taken: sine-Gordon and $\phi^{4}$-deformed. The geometrical coupling is used to produce a localized zero mode. Moreover, we analyze the massive spectrum for both fields and obtain possible resonant massive modes. Furthermore, we do not find tachyonic modes leading to a consistent thick brane. |
1606.01330 | Sumanta Chakraborty | Naresh Dadhich and Sumanta Chakraborty | Buchdahl compactness limit for a pure Lovelock static fluid star | Revised; Title Changed; 11 pages; no figures | Phys. Rev. D 95, 064059 (2017) | 10.1103/PhysRevD.95.064059 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain the Buchdahl compactness limit for a pure Lovelock static fluid
star and verify that the limit following from the uniform density
Schwarzschild's interior solution, which is universal irrespective of the
gravitational theory (Einstein or Lovelock), is true in general. In terms of
surface potential $\Phi(r)$, it means at the surface of the star $r=r_{0}$,
$\Phi(r_{0}) < 2N(d-N-1)/(d-1)^2$ where $d$, $N$ respectively indicate
spacetime dimensions and Lovelock order. For a given $N$, $\Phi(r_{0})$ is
maximum for $d=2N+2$ while it is always $4/9$, Buchdahl's limit, for $d=3N+1$.
It is also remarkable that for $N=1$ Einstein gravity, or for pure Lovelock in
$d=3N+1$, Buchdahl's limit is equivalent to the criteria that gravitational
field energy exterior to the star is less than half its gravitational mass,
having no reference to the interior at all.
| [
{
"created": "Sat, 4 Jun 2016 06:01:10 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Nov 2016 07:08:28 GMT",
"version": "v2"
},
{
"created": "Mon, 3 Apr 2017 04:52:30 GMT",
"version": "v3"
},
{
"created": "Mon, 5 Jun 2017 09:33:53 GMT",
"version": "v4"
}
] | 2017-06-06 | [
[
"Dadhich",
"Naresh",
""
],
[
"Chakraborty",
"Sumanta",
""
]
] | We obtain the Buchdahl compactness limit for a pure Lovelock static fluid star and verify that the limit following from the uniform density Schwarzschild's interior solution, which is universal irrespective of the gravitational theory (Einstein or Lovelock), is true in general. In terms of surface potential $\Phi(r)$, it means at the surface of the star $r=r_{0}$, $\Phi(r_{0}) < 2N(d-N-1)/(d-1)^2$ where $d$, $N$ respectively indicate spacetime dimensions and Lovelock order. For a given $N$, $\Phi(r_{0})$ is maximum for $d=2N+2$ while it is always $4/9$, Buchdahl's limit, for $d=3N+1$. It is also remarkable that for $N=1$ Einstein gravity, or for pure Lovelock in $d=3N+1$, Buchdahl's limit is equivalent to the criteria that gravitational field energy exterior to the star is less than half its gravitational mass, having no reference to the interior at all. |
gr-qc/9611069 | Juan Ayon | Eloy Ay\'on-Beato (Depto. Fisica, CINVESTAV-IPN, Mexico) | No-Hair Theorem for Spontaneously Broken Abelian Models in Static Black
Holes | 8 pages, 2 figures, RevTeX; some changes to match published version | Phys.Rev. D62 (2000) 104004 | 10.1103/PhysRevD.62.104004 | null | gr-qc hep-th | null | The vanishing of the electromagnetic field, for purely electric
configurations of spontaneously broken Abelian models, is established in the
domain of outer communications of a static asymptotically flat black hole. The
proof is gauge invariant, and is accomplished without any dependence on the
model. In the particular case of the Abelian Higgs model, it is shown that the
only solutions admitted for the scalar field become the vacuum expectation
values of the self-interaction.
| [
{
"created": "Thu, 28 Nov 1996 23:24:38 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Jul 2000 20:58:52 GMT",
"version": "v2"
},
{
"created": "Tue, 17 Oct 2000 17:58:15 GMT",
"version": "v3"
}
] | 2009-10-28 | [
[
"Ayón-Beato",
"Eloy",
"",
"Depto. Fisica, CINVESTAV-IPN, Mexico"
]
] | The vanishing of the electromagnetic field, for purely electric configurations of spontaneously broken Abelian models, is established in the domain of outer communications of a static asymptotically flat black hole. The proof is gauge invariant, and is accomplished without any dependence on the model. In the particular case of the Abelian Higgs model, it is shown that the only solutions admitted for the scalar field become the vacuum expectation values of the self-interaction. |
gr-qc/0410116 | Nelson Pinto-Neto | Nelson Pinto-Neto and Paulo I. Trajtenberg | The Hamiltonian of Asymptotically Friedmann-Lemaitre-Robertson-Walker
Spacetimes | 12 pages, no figures | Gen.Rel.Grav. 36 (2004) 1871 | 10.1023/B:GERG.0000035956.87421.b6 | null | gr-qc | null | We obtain the correct hamiltonian which describes the dynamics of classes of
asymptotic open Friedmann-Lema\^{\i}tre-Robertson-Walker (FLRW) spacetimes,
which includes Tolman geometries. We calculate the surface term that has to be
added to the usual hamiltonian of General Relativity in order to obtain an
improved hamiltonian with well defined functional derivatives. For asymptotic
flat FLRW spaces, this surface term is zero, but for asymptotic negative
curvature FLRW spaces it is not null in general. In the particular case of the
Tolman geometries, they vanish. The surface term evaluated on a particular
solution of Einstein's equations may be viewed as the ``energy'' of this
solution with respect to the FLRW spacetime they approach asymptotically. Our
results are obtained for a matter content described by a dust fluid, but they
are valid for any perfect fluid, including the cosmological constant.
| [
{
"created": "Fri, 22 Oct 2004 19:44:07 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Pinto-Neto",
"Nelson",
""
],
[
"Trajtenberg",
"Paulo I.",
""
]
] | We obtain the correct hamiltonian which describes the dynamics of classes of asymptotic open Friedmann-Lema\^{\i}tre-Robertson-Walker (FLRW) spacetimes, which includes Tolman geometries. We calculate the surface term that has to be added to the usual hamiltonian of General Relativity in order to obtain an improved hamiltonian with well defined functional derivatives. For asymptotic flat FLRW spaces, this surface term is zero, but for asymptotic negative curvature FLRW spaces it is not null in general. In the particular case of the Tolman geometries, they vanish. The surface term evaluated on a particular solution of Einstein's equations may be viewed as the ``energy'' of this solution with respect to the FLRW spacetime they approach asymptotically. Our results are obtained for a matter content described by a dust fluid, but they are valid for any perfect fluid, including the cosmological constant. |
1311.0389 | Ikjyot Singh Kohli | Ikjyot Singh Kohli and Michael C. Haslam | On The Dynamics of a Closed Viscous Universe | null | PhysRevD.89.043518 (2014) | 10.1103/PhysRevD.89.043518 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use a dynamical systems approach based on the method of orthonormal frames
to study the dynamics of a non-tilted Bianchi Type IX cosmological model with a
bulk and shear viscous fluid source. We begin by completing a detailed
fix-point analysis which give the local sinks, sources and saddles of the
dynamical system. We then analyze the global dynamics by finding the
$\alpha$-and $\omega$-limit sets which give an idea of the past and future
asymptotic behavior of the system. The fixed points were found to be a flat
Friedmann-LeMa\^{i}tre-Robertson-Walker (FLRW) solution, Bianchi Type $II$
solution, Kasner circle, Jacobs disc, Bianchi Type $VII_{0}$ solutions, and
several closed FLRW solutions in addition to the Einstein static universe
solution. Each equilibrium point was described in both its expanding and
contracting epochs. We conclude the paper with some numerical experiments that
shed light on the global dynamics of the system along with its heteroclinic
orbits. With respect to past asymptotic states, we were able to conclude that
the Jacobs disc in the expanding epoch was a source of the system along with
the flat FLRW solution in a contracting epoch. With respect to future
asymptotic states, we were able to show that the flat FLRW solution in an
expanding epoch along with the Jacobs disc in the contracting epoch were sinks
of the system. We were also able to demonstrate a new result with respect to
the Einstein static universe. Namely, we gave certain conditions on the
parameter space such that the Einstein static universe has an associated stable
subspace. We were however, not able to conclusively say anything about whether
a closed FLRW model could be a past or future asymptotic state of the model.
| [
{
"created": "Sat, 2 Nov 2013 16:25:27 GMT",
"version": "v1"
},
{
"created": "Sun, 10 Nov 2013 18:17:13 GMT",
"version": "v2"
},
{
"created": "Thu, 21 Nov 2013 17:15:47 GMT",
"version": "v3"
},
{
"created": "Mon, 24 Feb 2014 21:46:22 GMT",
"version": "v4"
},
{
"created": "Mon, 17 Mar 2014 18:05:04 GMT",
"version": "v5"
}
] | 2014-04-03 | [
[
"Kohli",
"Ikjyot Singh",
""
],
[
"Haslam",
"Michael C.",
""
]
] | We use a dynamical systems approach based on the method of orthonormal frames to study the dynamics of a non-tilted Bianchi Type IX cosmological model with a bulk and shear viscous fluid source. We begin by completing a detailed fix-point analysis which give the local sinks, sources and saddles of the dynamical system. We then analyze the global dynamics by finding the $\alpha$-and $\omega$-limit sets which give an idea of the past and future asymptotic behavior of the system. The fixed points were found to be a flat Friedmann-LeMa\^{i}tre-Robertson-Walker (FLRW) solution, Bianchi Type $II$ solution, Kasner circle, Jacobs disc, Bianchi Type $VII_{0}$ solutions, and several closed FLRW solutions in addition to the Einstein static universe solution. Each equilibrium point was described in both its expanding and contracting epochs. We conclude the paper with some numerical experiments that shed light on the global dynamics of the system along with its heteroclinic orbits. With respect to past asymptotic states, we were able to conclude that the Jacobs disc in the expanding epoch was a source of the system along with the flat FLRW solution in a contracting epoch. With respect to future asymptotic states, we were able to show that the flat FLRW solution in an expanding epoch along with the Jacobs disc in the contracting epoch were sinks of the system. We were also able to demonstrate a new result with respect to the Einstein static universe. Namely, we gave certain conditions on the parameter space such that the Einstein static universe has an associated stable subspace. We were however, not able to conclusively say anything about whether a closed FLRW model could be a past or future asymptotic state of the model. |
2303.04868 | Simen Braeck | S. Braeck | Inertial Frame Dragging and Relative Rotation of ZAMOs in Axistationary
Asymptotically Flat Spacetimes | 11 pages, 3 figures. This paper is a contribution to the Special
Issue of Universe "Entropy, Cosmic Inflation and the Theory of Relativity: In
Honour of Prof. {\O}yvind Gr{\o}n" | Universe 9, 120 (2023) | 10.3390/universe9030120 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In axistationary asymptotically flat spacetimes zero angular momentum
observers (ZAMOs) define an absolute standard of non--rotation locally, as can
be verified by the absence of any Sagnac effect for these observers.
Nevertheless, we argue that on a global scale the only physically meaningful
concept is that of relative rotation. The argument is substantiated by solving
Einstein's equations for an approximate thin shell model where we keep a degree
of freedom by relaxing the natural assumption of vanishing rotation at
asymptotic infinity at the outset of the analysis. The solution reveals that
Einstein's equations only determine differences in the rotation rate of ZAMOs,
thereby establishing the concept of relative rotation globally. The
interpretation of rotation as relative in a global context is inherently linked
to the freedom to transform between coordinate systems rotating relative to
each other, implying that an arbitrary ZAMO located at any radius may claim to
be the one who is non--rotating on a global scale and that the notion of an
asymptotic Lorentz frame relative to which one may measure absolute rotation is
devoid of any meaning. The concept of rotation in Kerr spacetime is then
briefly discussed in the context of this interpretation.
| [
{
"created": "Wed, 8 Mar 2023 20:20:42 GMT",
"version": "v1"
}
] | 2023-03-10 | [
[
"Braeck",
"S.",
""
]
] | In axistationary asymptotically flat spacetimes zero angular momentum observers (ZAMOs) define an absolute standard of non--rotation locally, as can be verified by the absence of any Sagnac effect for these observers. Nevertheless, we argue that on a global scale the only physically meaningful concept is that of relative rotation. The argument is substantiated by solving Einstein's equations for an approximate thin shell model where we keep a degree of freedom by relaxing the natural assumption of vanishing rotation at asymptotic infinity at the outset of the analysis. The solution reveals that Einstein's equations only determine differences in the rotation rate of ZAMOs, thereby establishing the concept of relative rotation globally. The interpretation of rotation as relative in a global context is inherently linked to the freedom to transform between coordinate systems rotating relative to each other, implying that an arbitrary ZAMO located at any radius may claim to be the one who is non--rotating on a global scale and that the notion of an asymptotic Lorentz frame relative to which one may measure absolute rotation is devoid of any meaning. The concept of rotation in Kerr spacetime is then briefly discussed in the context of this interpretation. |
gr-qc/0405058 | \'Etienne Racine | \'Etienne Racine | Spin and energy evolution equations for a wide class of extended bodies | 17 pages, no figure; substantial changes to presentation, cleaner
computational method and a reference added; version published in Class.
Quantum Grav | Class.Quant.Grav. 23 (2006) 373-390 | 10.1088/0264-9381/23/2/007 | null | gr-qc | null | We give a surface integral derivation of the leading-order evolution
equations for the spin and energy of a relativistic body interacting with other
bodies in the post-Newtonian expansion scheme. The bodies can be arbitrarily
shaped and can be strongly self-gravitating. The effects of all mass and
current multipoles are taken into account. As part of the computation one of
the 2PN potentials parametrizing the metric is obtained. The formulae obtained
here for spin and energy evolution coincide with those obtained by Damour,
Soffel and Xu for the case of weakly self-gravitating bodies. By combining an
Einstein-Infeld-Hoffman-type surface integral approach with multipolar
expansions we extend the domain of validity of these evolution equations to a
wide class of strongly self-gravitating bodies. This paper completes in a
self-contained way a previous work by Racine and Flanagan on translational
equations of motion for compact objects.
| [
{
"created": "Tue, 11 May 2004 18:41:57 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Dec 2005 21:53:39 GMT",
"version": "v2"
}
] | 2016-08-16 | [
[
"Racine",
"Étienne",
""
]
] | We give a surface integral derivation of the leading-order evolution equations for the spin and energy of a relativistic body interacting with other bodies in the post-Newtonian expansion scheme. The bodies can be arbitrarily shaped and can be strongly self-gravitating. The effects of all mass and current multipoles are taken into account. As part of the computation one of the 2PN potentials parametrizing the metric is obtained. The formulae obtained here for spin and energy evolution coincide with those obtained by Damour, Soffel and Xu for the case of weakly self-gravitating bodies. By combining an Einstein-Infeld-Hoffman-type surface integral approach with multipolar expansions we extend the domain of validity of these evolution equations to a wide class of strongly self-gravitating bodies. This paper completes in a self-contained way a previous work by Racine and Flanagan on translational equations of motion for compact objects. |
gr-qc/9504014 | Peter Peldan | Peter Peldan (Penn State University) | A Modular Invariant Quantum Theory From the Connection Formulation of
(2+1)-Gravity on the Torus | Latex, 4 pages | Class.Quant.Grav. 13 (1996) 221-224 | 10.1088/0264-9381/13/2/010 | CGPG-95/4-2 | gr-qc hep-th | null | By choosing an unconventional polarization of the connection phase space in
(2+1)-gravity on the torus, a modular invariant quantum theory is constructed.
Unitary equivalence to the ADM-quantization is shown.
| [
{
"created": "Mon, 10 Apr 1995 17:31:11 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Peldan",
"Peter",
"",
"Penn State University"
]
] | By choosing an unconventional polarization of the connection phase space in (2+1)-gravity on the torus, a modular invariant quantum theory is constructed. Unitary equivalence to the ADM-quantization is shown. |
0804.4784 | J. Fernando Barbero G. | J. Fernando Barbero G., Eduardo J. S. Villase\~nor | Generating functions for black hole entropy in Loop Quantum Gravity | nine pages | Phys.Rev.D77:121502,2008 | 10.1103/PhysRevD.77.121502 | null | gr-qc math-ph math.CO math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce, in a systematic way, a set of generating functions that solve
all the different combinatorial problems that crop up in the study of black
hole entropy in Loop Quantum Gravity. Specifically we give generating functions
for: The different sources of degeneracy related to the spectrum of the area
operator, the solutions to the projection constraint, and the black hole
degeneracy spectrum. Our methods are capable of handling the different
countings proposed and discussed in the literature. The generating functions
presented here provide the appropriate starting point to extend the results
already obtained for microscopic black holes to the macroscopic regime --in
particular those concerning the area law and the appearance of an effectively
equidistant area spectrum.
| [
{
"created": "Wed, 30 Apr 2008 10:42:42 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"G.",
"J. Fernando Barbero",
""
],
[
"Villaseñor",
"Eduardo J. S.",
""
]
] | We introduce, in a systematic way, a set of generating functions that solve all the different combinatorial problems that crop up in the study of black hole entropy in Loop Quantum Gravity. Specifically we give generating functions for: The different sources of degeneracy related to the spectrum of the area operator, the solutions to the projection constraint, and the black hole degeneracy spectrum. Our methods are capable of handling the different countings proposed and discussed in the literature. The generating functions presented here provide the appropriate starting point to extend the results already obtained for microscopic black holes to the macroscopic regime --in particular those concerning the area law and the appearance of an effectively equidistant area spectrum. |
1110.6880 | Michael Sachs | Michael K. Sachs | Testing Lattice Quantum Gravity in 2+1 Dimensions | 13 pages, 11 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Borrowing techniques from cosmology, I compute the power spectrum of quantum
fluctuations in (2+1)-dimensional causal dynamical triangulations, a promising
discrete path integral approach to quantum gravity. The results agree with
those of canonical quantization to a high degree of precision, providing strong
evidence for the equivalence of the two approaches and for the validity of the
discrete method.
| [
{
"created": "Mon, 31 Oct 2011 18:12:59 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Nov 2011 23:38:44 GMT",
"version": "v2"
}
] | 2011-11-03 | [
[
"Sachs",
"Michael K.",
""
]
] | Borrowing techniques from cosmology, I compute the power spectrum of quantum fluctuations in (2+1)-dimensional causal dynamical triangulations, a promising discrete path integral approach to quantum gravity. The results agree with those of canonical quantization to a high degree of precision, providing strong evidence for the equivalence of the two approaches and for the validity of the discrete method. |
gr-qc/0506076 | Athanasios Prikas | Athanasios Prikas | Q-stars in scalar-tensor gravitational theories | 14 pages, to appear in Phys. Lett. B | Phys.Lett. B620 (2005) 88-96 | 10.1016/j.physletb.2005.06.022 | null | gr-qc | null | We study q-stars in Brans-Dicke gravitational theory. We find that when the
Brans-Dicke constant, $\omega_{\textrm{BD}}$, tends to infinity, the results of
General Relativity are reproduced. For other values of $\omega_{\textrm{BD}}$,
the particle number, mass and radius of the star and the absolute value of the
matter field are a few percent larger than in the case of General Relativity.
We also investigate the general scalar-tensor gravitational theory and find
that the star parameters are a few percent larger than in the case of General
Relativity.
| [
{
"created": "Sun, 12 Jun 2005 18:50:51 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Prikas",
"Athanasios",
""
]
] | We study q-stars in Brans-Dicke gravitational theory. We find that when the Brans-Dicke constant, $\omega_{\textrm{BD}}$, tends to infinity, the results of General Relativity are reproduced. For other values of $\omega_{\textrm{BD}}$, the particle number, mass and radius of the star and the absolute value of the matter field are a few percent larger than in the case of General Relativity. We also investigate the general scalar-tensor gravitational theory and find that the star parameters are a few percent larger than in the case of General Relativity. |
0711.4797 | Ulf Leonhardt | Thomas G. Philbin, Chris Kuklewicz, Scott Robertson, Stephen Hill,
Friedrich Konig, Ulf Leonhardt | Fiber-optical analogue of the event horizon: Appendices | null | null | null | null | gr-qc | null | We explain the theory behind our fiber-optical analogue of the event horizon
and present the experiment in detail.
| [
{
"created": "Thu, 29 Nov 2007 19:08:18 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Dec 2007 09:58:47 GMT",
"version": "v2"
}
] | 2007-12-13 | [
[
"Philbin",
"Thomas G.",
""
],
[
"Kuklewicz",
"Chris",
""
],
[
"Robertson",
"Scott",
""
],
[
"Hill",
"Stephen",
""
],
[
"Konig",
"Friedrich",
""
],
[
"Leonhardt",
"Ulf",
""
]
] | We explain the theory behind our fiber-optical analogue of the event horizon and present the experiment in detail. |
1406.7375 | Panagiotis Iosif | Panagiotis Iosif and Nikolaos Stergioulas | On the accuracy of the IWM-CFC approximation in differentially rotating
relativistic stars | 12 pages, 5 figures, 2 tables, updated to match version accepted for
publication in General Relativity and Gravitation | null | 10.1007/s10714-014-1800-5 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We determine the accuracy of the conformal flatness (IWM-CFC) approximation
for the case of single, but strongly differentially rotating relativistic
stars. We find that for the fastest rotating and most relativistic polytropic
models, the deviation from full general relativity is below 5% for integrated
quantities and below 10% for local quantities, such as the angular velocity.
Furthermore, we study the deviation of the IWM-CFC approximation from full
general relativity by evaluating and comparing different error indicators. We
find that for the models that are not near the maximum mass, a simple error
indicator constructed from local values of the metric potentials is more
indicative of the accuracy of the IWM-CFC approximation than an error indicator
that is based on the Cotton-York tensor. Furthermore, we construct a simple,
linear empirical relation that allows for the estimation of the error made by
the IWM-CFC approximation and which only involves the flattening of the star
due to rotation and the minimum value of the lapse function. Thus, in any
numerical simulation involving rotating relativistic stars, one can readily
know the deviations from full general relativity due to the IWM-CFC
approximation.
| [
{
"created": "Sat, 28 Jun 2014 09:15:53 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Sep 2014 12:34:50 GMT",
"version": "v2"
}
] | 2014-09-23 | [
[
"Iosif",
"Panagiotis",
""
],
[
"Stergioulas",
"Nikolaos",
""
]
] | We determine the accuracy of the conformal flatness (IWM-CFC) approximation for the case of single, but strongly differentially rotating relativistic stars. We find that for the fastest rotating and most relativistic polytropic models, the deviation from full general relativity is below 5% for integrated quantities and below 10% for local quantities, such as the angular velocity. Furthermore, we study the deviation of the IWM-CFC approximation from full general relativity by evaluating and comparing different error indicators. We find that for the models that are not near the maximum mass, a simple error indicator constructed from local values of the metric potentials is more indicative of the accuracy of the IWM-CFC approximation than an error indicator that is based on the Cotton-York tensor. Furthermore, we construct a simple, linear empirical relation that allows for the estimation of the error made by the IWM-CFC approximation and which only involves the flattening of the star due to rotation and the minimum value of the lapse function. Thus, in any numerical simulation involving rotating relativistic stars, one can readily know the deviations from full general relativity due to the IWM-CFC approximation. |
1302.5217 | Vladimir Folomeev | Vladimir Dzhunushaliev, Vladimir Folomeev, Burkhard Kleihaus, Jutta
Kunz | Mixed neutron-star-plus-wormhole systems: Linear stability analysis | 15 pages, 4 figures, minor corrections to content, references added,
version published in PRD | Phys. Rev. D 87, 104036 (2013) | 10.1103/PhysRevD.87.104036 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider configurations consisting of a neutron star with a wormhole at
the core. The wormhole is held open by a ghost scalar field with a quartic
coupling. The neutron matter is described by a perfect fluid with a polytropic
equation of state. We obtain static regular solutions for these systems. A
stability analysis, however, shows that they are unstable with respect to
linear perturbations.
| [
{
"created": "Thu, 21 Feb 2013 08:56:58 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Jun 2013 11:11:44 GMT",
"version": "v2"
}
] | 2013-06-04 | [
[
"Dzhunushaliev",
"Vladimir",
""
],
[
"Folomeev",
"Vladimir",
""
],
[
"Kleihaus",
"Burkhard",
""
],
[
"Kunz",
"Jutta",
""
]
] | We consider configurations consisting of a neutron star with a wormhole at the core. The wormhole is held open by a ghost scalar field with a quartic coupling. The neutron matter is described by a perfect fluid with a polytropic equation of state. We obtain static regular solutions for these systems. A stability analysis, however, shows that they are unstable with respect to linear perturbations. |
gr-qc/9905091 | Mark Trodden | Mark Trodden and Tanmay Vachaspati | What is the Homogeneity of our Universe Telling Us? | 6 pages. Awarded Honorable Mention in the 1999 Gravity Research
Foundation Essay Competition | Mod.Phys.Lett. A14 (1999) 1661-1666 | 10.1142/S0217732399001747 | CWRU-P20-99 | gr-qc astro-ph | null | The universe we observe is homogeneous on super-horizon scales, leading to
the ``cosmic homogeneity problem''. Inflation alleviates this problem but
cannot solve it within the realm of conservative extrapolations of classical
physics. A probabilistic solution of the problem is possible but is subject to
interpretational difficulties. A genuine deterministic solution of the
homogeneity problem requires radical departures from known physics.
| [
{
"created": "Mon, 24 May 1999 16:27:44 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Trodden",
"Mark",
""
],
[
"Vachaspati",
"Tanmay",
""
]
] | The universe we observe is homogeneous on super-horizon scales, leading to the ``cosmic homogeneity problem''. Inflation alleviates this problem but cannot solve it within the realm of conservative extrapolations of classical physics. A probabilistic solution of the problem is possible but is subject to interpretational difficulties. A genuine deterministic solution of the homogeneity problem requires radical departures from known physics. |
2211.11585 | Mariano Cadoni | M. Cadoni, M. De Laurentis, I. De Martino, R. Della Monica, M. Oi, and
A. P. Sanna | Are nonsingular black holes with super-Planckian hair ruled out by S2
star data? | 6 pages, 2 figures, 1 table. Revised version: Addendum and some
references have been added | null | 10.1103/PhysRevD.107.044038 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | We propose a novel nonsingular black-hole spacetime representing a strong
deformation of the Schwarzschild solution with mass $M$ by an additional hair
$\ell$, which may be hierarchically larger than the Planck scale. Our
black-hole model presents a de Sitter core and $\mathcal{O}(\ell^2/r^2)$
slow-decaying corrections to the Schwarzschild solution. Our black-hole
solutions are thermodynamically preferred when $0.2 \lesssim \ell/GM \lesssim
\, 0.3$ and are characterized by strong deviations in the orbits of test
particles from the Schwarzschild case. In particular, we find corrections to
the perihelion precession angle scaling linearly with $\ell$. We test our model
using the available data for the orbits of the S2 star around $\text{SgrA}^*$.
These data strongly constrain the value of the hair $\ell$, casting an upper
bound on it of $\sim \, 0.47 \, GM$, but do not rule out the possible existence
of regular black holes with super-Planckian hair.
| [
{
"created": "Mon, 21 Nov 2022 15:38:12 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Nov 2022 11:06:00 GMT",
"version": "v2"
}
] | 2023-03-01 | [
[
"Cadoni",
"M.",
""
],
[
"De Laurentis",
"M.",
""
],
[
"De Martino",
"I.",
""
],
[
"Della Monica",
"R.",
""
],
[
"Oi",
"M.",
""
],
[
"Sanna",
"A. P.",
""
]
] | We propose a novel nonsingular black-hole spacetime representing a strong deformation of the Schwarzschild solution with mass $M$ by an additional hair $\ell$, which may be hierarchically larger than the Planck scale. Our black-hole model presents a de Sitter core and $\mathcal{O}(\ell^2/r^2)$ slow-decaying corrections to the Schwarzschild solution. Our black-hole solutions are thermodynamically preferred when $0.2 \lesssim \ell/GM \lesssim \, 0.3$ and are characterized by strong deviations in the orbits of test particles from the Schwarzschild case. In particular, we find corrections to the perihelion precession angle scaling linearly with $\ell$. We test our model using the available data for the orbits of the S2 star around $\text{SgrA}^*$. These data strongly constrain the value of the hair $\ell$, casting an upper bound on it of $\sim \, 0.47 \, GM$, but do not rule out the possible existence of regular black holes with super-Planckian hair. |
gr-qc/0404053 | Julio Cesar Fabris | J.C. Fabris, S.V.B. Goncalves and M.S. dos Santos | Gravitational waves in the generalized Chaplygin gas model | Latex file, 9 pages, 11 figures eps format | Gen.Rel.Grav. 36 (2004) 2559-2572 | 10.1023/B:GERG.0000046854.75501.bf | null | gr-qc astro-ph | null | The consequences of taking the generalized Chaplygin gas as the dark energy
constituent of the Universe on the gravitational waves are studied and the
spectrum obtained from this model, for the flat case, is analyzed. Besides its
importance for the study of the primordial Universe, the gravitational waves
represent an additional perspective (besides the CMB temperature and
polarization anisotropies) to evaluate the consistence of the different dark
energy models and establish better constraints to their parameters. The
analysis presented here takes this fact into consideration to open one more
perspective of verification of the generalized Chapligin gas model
applicability. Nine particular cases are compared: one where no dark energy is
present; two that simulate the $\Lambda$-CDM model; two where the gas acts like
the traditional Chaplygin gas; and four where the dark energy is the
generalized Chaplygin gas. The different spectra permit to distinguish the
$\Lambda$-CDM and the Chaplygin gas scenarios.
| [
{
"created": "Mon, 12 Apr 2004 22:02:08 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Fabris",
"J. C.",
""
],
[
"Goncalves",
"S. V. B.",
""
],
[
"Santos",
"M. S. dos",
""
]
] | The consequences of taking the generalized Chaplygin gas as the dark energy constituent of the Universe on the gravitational waves are studied and the spectrum obtained from this model, for the flat case, is analyzed. Besides its importance for the study of the primordial Universe, the gravitational waves represent an additional perspective (besides the CMB temperature and polarization anisotropies) to evaluate the consistence of the different dark energy models and establish better constraints to their parameters. The analysis presented here takes this fact into consideration to open one more perspective of verification of the generalized Chapligin gas model applicability. Nine particular cases are compared: one where no dark energy is present; two that simulate the $\Lambda$-CDM model; two where the gas acts like the traditional Chaplygin gas; and four where the dark energy is the generalized Chaplygin gas. The different spectra permit to distinguish the $\Lambda$-CDM and the Chaplygin gas scenarios. |
gr-qc/0203069 | cherubini Christian | Donato Bini, Christian Cherubini, Robert T Jantzen, Remo J. Ruffini | Teukolsky Master Equation: De Rham wave equation for the gravitational
and electromagnetic fields in vacuum | 30 pages. No figures. Used PTP macros. To appear on Prog. Theor.
Phys., Vol. 107, No. 5, May 2002 | Prog.Theor.Phys. 107 (2002) 967-992 | 10.1143/PTP.107.967 | null | gr-qc | null | A new version of the Teukolksy Master Equation, describing any massless field
of different spin $s=1/2,1,3/2,2$ in the Kerr black hole, is presented here in
the form of a wave equation containing additional curvature terms. These
results suggest a relation between curvature perturbation theory in general
relativity and the exact wave equations satisfied by the Weyl and the Maxwell
tensors, known in the literature as the de Rham-Lichnerowicz Laplacian
equations. We discuss these Laplacians both in the Newman-Penrose formalism and
in the Geroch-Held-Penrose variant for an arbitrary vacuum spacetime.
Perturbative expansion of these wave equations results in a recursive scheme
valid for higher orders. This approach, apart from the obvious implications for
the gravitational and electromagnetic wave propagation on a curved spacetime,
explains and extends the results in the literature for perturbative analysis by
clarifying their true origins in the exact theory.
| [
{
"created": "Thu, 21 Mar 2002 11:54:53 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Bini",
"Donato",
""
],
[
"Cherubini",
"Christian",
""
],
[
"Jantzen",
"Robert T",
""
],
[
"Ruffini",
"Remo J.",
""
]
] | A new version of the Teukolksy Master Equation, describing any massless field of different spin $s=1/2,1,3/2,2$ in the Kerr black hole, is presented here in the form of a wave equation containing additional curvature terms. These results suggest a relation between curvature perturbation theory in general relativity and the exact wave equations satisfied by the Weyl and the Maxwell tensors, known in the literature as the de Rham-Lichnerowicz Laplacian equations. We discuss these Laplacians both in the Newman-Penrose formalism and in the Geroch-Held-Penrose variant for an arbitrary vacuum spacetime. Perturbative expansion of these wave equations results in a recursive scheme valid for higher orders. This approach, apart from the obvious implications for the gravitational and electromagnetic wave propagation on a curved spacetime, explains and extends the results in the literature for perturbative analysis by clarifying their true origins in the exact theory. |
2309.16944 | Chao-Jun Feng | Ke Wang, Chao-Jun Feng, Towe Wang | Image of Kerr-de Sitter black holes illuminated by equatorial thin
accretion disks | 17 pages, 10 figures, refs added, typos corrected | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | To explore the influence of the cosmological constant on black hole images,
we have developed a comprehensive analytical method for simulating images of
Kerr-de Sitter black holes illuminated by equatorial thin accretion disks.
Through the application of explicit equations, we simulate images of Kerr-de
Sitter black holes illuminated by both prograde and retrograde accretion disks,
examining the impact of the cosmological constant on their characteristic
curves, relative sizes, and observed intensities. Our findings reveal that, in
comparison to Kerr black holes, the cosmological constant not only diminishes
the relative size of a black hole but also amplifies its luminosity. Moreover,
an observer's relative position in the universe ($r_0/r_C$) can influence both
the relative size and luminosity of a black hole, where $r_0$ is the distance
from the observer to the black hole, $r_C$ is the cosmological horizon
determined by the value of the cosmological constant $\Lambda$.
| [
{
"created": "Fri, 29 Sep 2023 03:02:57 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Dec 2023 08:55:18 GMT",
"version": "v2"
},
{
"created": "Tue, 19 Dec 2023 04:17:51 GMT",
"version": "v3"
},
{
"created": "Tue, 30 Apr 2024 07:14:13 GMT",
"version": "v4"
}
] | 2024-05-01 | [
[
"Wang",
"Ke",
""
],
[
"Feng",
"Chao-Jun",
""
],
[
"Wang",
"Towe",
""
]
] | To explore the influence of the cosmological constant on black hole images, we have developed a comprehensive analytical method for simulating images of Kerr-de Sitter black holes illuminated by equatorial thin accretion disks. Through the application of explicit equations, we simulate images of Kerr-de Sitter black holes illuminated by both prograde and retrograde accretion disks, examining the impact of the cosmological constant on their characteristic curves, relative sizes, and observed intensities. Our findings reveal that, in comparison to Kerr black holes, the cosmological constant not only diminishes the relative size of a black hole but also amplifies its luminosity. Moreover, an observer's relative position in the universe ($r_0/r_C$) can influence both the relative size and luminosity of a black hole, where $r_0$ is the distance from the observer to the black hole, $r_C$ is the cosmological horizon determined by the value of the cosmological constant $\Lambda$. |
1612.00974 | Gabriel Farrugia | Gabriel Farrugia, Jackson Levi Said | Growth factor in $f(T,\mathcal{T})$ gravity | 21 pages, 12 figures | Phys. Rev. D 94, 124004 (2016) | 10.1103/PhysRevD.94.124004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the growth factor for sub-horizon modes during late times in
$f(T,\mathcal{T})$ gravity, where $T$ is the torsion scalar and $\mathcal{T}$
is the trace of the stress-energy tensor. This is achieved by obtaining the
modified M\'{e}sz\'{a}ros equation, which describes the evolution of the
perturbations of the matter energy density, and obtaining numerical results.
Such results are obtained by solving the modified continuity equation and
analysing the behaviour of the solutions of the latter using various
constraints on the integration constants. Furthermore, the role of the
anisotropic term $\pi^{S}$ is investigated.
| [
{
"created": "Sat, 3 Dec 2016 15:42:24 GMT",
"version": "v1"
}
] | 2016-12-06 | [
[
"Farrugia",
"Gabriel",
""
],
[
"Said",
"Jackson Levi",
""
]
] | We investigate the growth factor for sub-horizon modes during late times in $f(T,\mathcal{T})$ gravity, where $T$ is the torsion scalar and $\mathcal{T}$ is the trace of the stress-energy tensor. This is achieved by obtaining the modified M\'{e}sz\'{a}ros equation, which describes the evolution of the perturbations of the matter energy density, and obtaining numerical results. Such results are obtained by solving the modified continuity equation and analysing the behaviour of the solutions of the latter using various constraints on the integration constants. Furthermore, the role of the anisotropic term $\pi^{S}$ is investigated. |
1012.5605 | Farook Rahaman | A A Usmani, Farook Rahaman, Saibal Ray, K K Nandi, Peter K. F.
Kuhfittig, Sk. A Rakib, Z Hasan | Charged gravastars admitting conformal motion | Minor addition, Accepted in Phys. Lett. B | null | 10.1016/j.physletb.2011.06.001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a new model of a {\it gravastar} admitting conformal motion. While
retaining the framework of the Mazur-Mottola model, the gravastar is assumed to
be internally charged, with an exterior defined by a Reissner-Nordstr{\"o}m
rather than a Schwarzschild line element. The solutions obtained involve (i)
the interior region, (ii) the shell, and (iii) the exterior region of the
sphere. Of these three cases the first case is of primary interest since the
total gravitational mass vanishes for vanishing charge and turns the total
gravitational mass into an {\it electromagnetic mass} under certain conditions.
This suggests that the interior de Sitter vacuum of a charged gravastar is
essentially an electromagnetic mass model that must generate the gravitational
mass. We have also analyzed various other aspects such as the stress energy
tensor in the thin shell and the entropy of the system.
| [
{
"created": "Mon, 27 Dec 2010 12:34:00 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Jun 2011 16:08:26 GMT",
"version": "v2"
}
] | 2011-06-06 | [
[
"Usmani",
"A A",
""
],
[
"Rahaman",
"Farook",
""
],
[
"Ray",
"Saibal",
""
],
[
"Nandi",
"K K",
""
],
[
"Kuhfittig",
"Peter K. F.",
""
],
[
"Rakib",
"Sk. A",
""
],
[
"Hasan",
"Z",
""
]
] | We propose a new model of a {\it gravastar} admitting conformal motion. While retaining the framework of the Mazur-Mottola model, the gravastar is assumed to be internally charged, with an exterior defined by a Reissner-Nordstr{\"o}m rather than a Schwarzschild line element. The solutions obtained involve (i) the interior region, (ii) the shell, and (iii) the exterior region of the sphere. Of these three cases the first case is of primary interest since the total gravitational mass vanishes for vanishing charge and turns the total gravitational mass into an {\it electromagnetic mass} under certain conditions. This suggests that the interior de Sitter vacuum of a charged gravastar is essentially an electromagnetic mass model that must generate the gravitational mass. We have also analyzed various other aspects such as the stress energy tensor in the thin shell and the entropy of the system. |
0710.1562 | Torsten Asselmeyer-Maluga | Torsten Asselmeyer-Maluga and Helge Rose | Dark energy and 3-manifold topology | 7 pages, no figures | ActaPhys.Polon.B38:3633-3640,2007 | null | null | gr-qc | null | We show that the differential-geometric description of matter by differential
structures of spacetime leads to a unifying model of the three types of energy
in the cosmos: matter, dark matter and dark energy. Using this model we are
able to calculate the ratio of dark energy to the total energy of the cosmos.
| [
{
"created": "Mon, 8 Oct 2007 14:40:33 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Nov 2007 08:49:27 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Asselmeyer-Maluga",
"Torsten",
""
],
[
"Rose",
"Helge",
""
]
] | We show that the differential-geometric description of matter by differential structures of spacetime leads to a unifying model of the three types of energy in the cosmos: matter, dark matter and dark energy. Using this model we are able to calculate the ratio of dark energy to the total energy of the cosmos. |
2311.15019 | Hari K | Hari K, Subhajit Barman and Dawood Kothawala | Universal role of curvature in vacuum entanglement | Published in PRD, 28 pages and 15 figures | Phys. Rev. D 109 (2024) 6, 065017 | 10.1103/PhysRevD.109.065017 | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | We highlight some universal features concerning the role of spacetime
curvature in the entanglement induced between quantum probes coupled to a
quantum field in a suitable vacuum state. The probes are initially causally
disconnected and non-entangled. We explore the parameter space $\{{\omega},
d_0, \boldsymbol{v}_0\}$ spanned by the energy gap $\omega$ of the detectors,
and the initial values of separation distance $d_0$ and relative velocity
$\boldsymbol{v}_0$, both covariantly defined in arbitrary curved spacetime. We
also obtain numerical results in de Sitter spacetimes and use these to explore
strong curvature regime, while also corroborating our perturbative results in
arbitrary curved spacetime. Our analysis shows that curvature can induce
entanglement features in certain regions of the above parameter space, in a
manner which facilitates using entanglement as a probe of spacetime curvature.
| [
{
"created": "Sat, 25 Nov 2023 13:14:33 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Mar 2024 08:31:58 GMT",
"version": "v2"
}
] | 2024-03-20 | [
[
"K",
"Hari",
""
],
[
"Barman",
"Subhajit",
""
],
[
"Kothawala",
"Dawood",
""
]
] | We highlight some universal features concerning the role of spacetime curvature in the entanglement induced between quantum probes coupled to a quantum field in a suitable vacuum state. The probes are initially causally disconnected and non-entangled. We explore the parameter space $\{{\omega}, d_0, \boldsymbol{v}_0\}$ spanned by the energy gap $\omega$ of the detectors, and the initial values of separation distance $d_0$ and relative velocity $\boldsymbol{v}_0$, both covariantly defined in arbitrary curved spacetime. We also obtain numerical results in de Sitter spacetimes and use these to explore strong curvature regime, while also corroborating our perturbative results in arbitrary curved spacetime. Our analysis shows that curvature can induce entanglement features in certain regions of the above parameter space, in a manner which facilitates using entanglement as a probe of spacetime curvature. |
2102.05519 | Shahar Hod | Shahar Hod | Hawking radiation may violate the Penrose cosmic censorship conjecture | 5 pages. This essay received an Honorable Mention from the Gravity
Research Foundation 2019 | International Journal of Modern Physics D 28, 1944023 (2019) | 10.1142/S0218271819440231 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | We analyze the Hawking evaporation process of Reissner-Nordstr\"om black
holes. It is shown that the characteristic radiation quanta emitted by the
charged black holes may turn near-extremal black-hole spacetimes into
horizonless naked singularities. The present analysis therefore reveals the
intriguing possibility that the semi-classical Hawking evaporation process of
black holes may violate the fundamental Penrose cosmic censorship conjecture.
| [
{
"created": "Wed, 10 Feb 2021 16:02:59 GMT",
"version": "v1"
}
] | 2021-02-17 | [
[
"Hod",
"Shahar",
""
]
] | We analyze the Hawking evaporation process of Reissner-Nordstr\"om black holes. It is shown that the characteristic radiation quanta emitted by the charged black holes may turn near-extremal black-hole spacetimes into horizonless naked singularities. The present analysis therefore reveals the intriguing possibility that the semi-classical Hawking evaporation process of black holes may violate the fundamental Penrose cosmic censorship conjecture. |
1008.2671 | S Habib Mazharimousavi | S. Habib Mazharimousavi and M. Halilsoy | Domain-Walls in Einstein-Gauss-Bonnet Bulk | 4 pages and 4 figures, to appear in PRD | Phys.Rev.D82:087502,2010 | 10.1103/PhysRevD.82.087502 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the dynamics of a d-dimensional domain wall (DW) in a
d+1-dimensional Einstein-Gauss-Bonnet (EGB) bulk. Exact effective potential
induced by the Gauss-Bonnet (GB) term on the wall is derived. In the absence of
the GB term we recover the familiar gravitational and anti-harmonic oscillator
potentials. Inclusion of the GB correction gives rise to a minimum radius of
bounce for the Friedmann-Robertson-Walker (FRW) universe expanding with a
negative pressure on the DW.
| [
{
"created": "Mon, 16 Aug 2010 14:37:44 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Sep 2010 19:27:51 GMT",
"version": "v2"
}
] | 2010-10-28 | [
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Halilsoy",
"M.",
""
]
] | We investigate the dynamics of a d-dimensional domain wall (DW) in a d+1-dimensional Einstein-Gauss-Bonnet (EGB) bulk. Exact effective potential induced by the Gauss-Bonnet (GB) term on the wall is derived. In the absence of the GB term we recover the familiar gravitational and anti-harmonic oscillator potentials. Inclusion of the GB correction gives rise to a minimum radius of bounce for the Friedmann-Robertson-Walker (FRW) universe expanding with a negative pressure on the DW. |
gr-qc/9806071 | null | Dan N. Vollick | Maintaining a Wormhole with a Scalar Field | 12 pages, LaTex | Phys.Rev. D56 (1997) 4724-4728 | 10.1103/PhysRevD.56.4724 | null | gr-qc | null | It is well known that it takes matter that violates the averaged weak energy
condition to hold the throat of a wormhole open. The production of such
``exotic'' matter is usually discussed within the context of quantum field
theory. In this paper I show that it is possible to produce the exotic matter
required to hold a wormhole open classically. This is accomplished by coupling
a scalar field to matter that satisfies the weak energy condition. The
energy-momentum tensor of the scalar field and the matter separately satisfy
the weak energy condition, but there exists an interaction energy-momentum
tensor that does not. It is this interaction energy-momentum tensor that allows
the wormhole to be maintained.
| [
{
"created": "Tue, 16 Jun 1998 19:57:39 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Vollick",
"Dan N.",
""
]
] | It is well known that it takes matter that violates the averaged weak energy condition to hold the throat of a wormhole open. The production of such ``exotic'' matter is usually discussed within the context of quantum field theory. In this paper I show that it is possible to produce the exotic matter required to hold a wormhole open classically. This is accomplished by coupling a scalar field to matter that satisfies the weak energy condition. The energy-momentum tensor of the scalar field and the matter separately satisfy the weak energy condition, but there exists an interaction energy-momentum tensor that does not. It is this interaction energy-momentum tensor that allows the wormhole to be maintained. |
2205.09147 | Leonardo Chataignier | Leonardo Chataignier | Beyond semiclassical time | null | Z.Naturforsch.A (2022) | 10.1515/zna-2022-0106 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the usual Born-Oppenheimer type of approximation used in quantum
gravity, in which a semiclassical time parameter emerges from a weak-coupling
expansion of the Wheeler-DeWitt constraint, leads to a unitary theory at least
up to the next-to-leading order in minisuperspace models. As there are no
unitarity-violating terms, this settles the issue of unitarity at this order,
which has been much debated in the literature. Furthermore, we also show that
the conserved inner product is gauge-fixed in the sense that the measure is
related to the Faddeev-Popov determinant associated with the choice of
semiclassical time as a reparametrization gauge. This implies that the
Born-Oppenheimer approach to the problem of time is, in fact, an instance of a
relational quantum theory, in which transition amplitudes can be related to
conditional probabilities.
| [
{
"created": "Wed, 18 May 2022 18:03:19 GMT",
"version": "v1"
}
] | 2022-05-20 | [
[
"Chataignier",
"Leonardo",
""
]
] | We show that the usual Born-Oppenheimer type of approximation used in quantum gravity, in which a semiclassical time parameter emerges from a weak-coupling expansion of the Wheeler-DeWitt constraint, leads to a unitary theory at least up to the next-to-leading order in minisuperspace models. As there are no unitarity-violating terms, this settles the issue of unitarity at this order, which has been much debated in the literature. Furthermore, we also show that the conserved inner product is gauge-fixed in the sense that the measure is related to the Faddeev-Popov determinant associated with the choice of semiclassical time as a reparametrization gauge. This implies that the Born-Oppenheimer approach to the problem of time is, in fact, an instance of a relational quantum theory, in which transition amplitudes can be related to conditional probabilities. |
0904.1562 | Lorenzo Iorio | Lorenzo Iorio | Constraints on planet X/Nemesis from Solar System's inner dynamics | LaTex, MNRAS macros. 12 pages, 4 figures, 3 tables. To appear in
Monthly Notices of the Royal Astronomical Society (MNRAS). Some typos fixed | Mon.Not.Roy.Astron.Soc.400:346-353,2009 | 10.1111/j.1365-2966.2009.15458.x | null | gr-qc astro-ph.EP physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We put full 3D constraints on a putative planet X by using the dynamics of
the inner planets of the solar system. In particular, we compute the mimium
distance of X as a function of its heliocentric latitude and longitude for
different values of its mass.
| [
{
"created": "Thu, 9 Apr 2009 17:02:58 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Apr 2009 12:43:34 GMT",
"version": "v2"
},
{
"created": "Sun, 17 May 2009 01:17:18 GMT",
"version": "v3"
},
{
"created": "Wed, 29 Jul 2009 11:10:48 GMT",
"version": "v4"
}
] | 2009-11-12 | [
[
"Iorio",
"Lorenzo",
""
]
] | We put full 3D constraints on a putative planet X by using the dynamics of the inner planets of the solar system. In particular, we compute the mimium distance of X as a function of its heliocentric latitude and longitude for different values of its mass. |
1609.02040 | Olivier Brunet | Olivier Brunet | Geometric Time and Causal Time in Relativistic Lagrangian Mechanics | null | null | null | null | gr-qc math-ph math.MP physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, we argue that two distinct types of time should be taken
into account in relativistic physics: a geometric time, which emanates from the
structure of spacetime and its metrics, and a causal time, indicating the flow
from the past to the future. A particularity of causal times is that its values
have no intrinsic meaning, as their evolution alone is meaningful. In the
context of relativistic Lagrangian mechanics, causal times corresponds to
admissible parameterizations of paths, and we show that in order for a
langragian to not depend on any particular causal time (as its values have no
intrinsic meaning), it has to be homogeneous in its velocity argument. We
illustrate this property with the example of a free particle in a potential.
Then, using a geometric Lagrangian (i.e. a parameterization independent
Lagrangian which is also manifestly covariant), we introduce the notion of
ageodesicity of a path which measures to what extent a path is far from being a
geodesic, and show how the notion can be used in the twin paradox to
differentiate the paths followed by the two twins.
| [
{
"created": "Tue, 6 Sep 2016 08:37:15 GMT",
"version": "v1"
}
] | 2016-09-08 | [
[
"Brunet",
"Olivier",
""
]
] | In this article, we argue that two distinct types of time should be taken into account in relativistic physics: a geometric time, which emanates from the structure of spacetime and its metrics, and a causal time, indicating the flow from the past to the future. A particularity of causal times is that its values have no intrinsic meaning, as their evolution alone is meaningful. In the context of relativistic Lagrangian mechanics, causal times corresponds to admissible parameterizations of paths, and we show that in order for a langragian to not depend on any particular causal time (as its values have no intrinsic meaning), it has to be homogeneous in its velocity argument. We illustrate this property with the example of a free particle in a potential. Then, using a geometric Lagrangian (i.e. a parameterization independent Lagrangian which is also manifestly covariant), we introduce the notion of ageodesicity of a path which measures to what extent a path is far from being a geodesic, and show how the notion can be used in the twin paradox to differentiate the paths followed by the two twins. |
1401.3578 | Claus Kiefer | Claus Kiefer | Conceptual Problems in Quantum Gravity and Quantum Cosmology | 41 pages, invited review | ISRN Math.Phys. 2013 (2013) 509316 | 10.1155/2013/509316 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The search for a consistent and empirically established quantum theory of
gravity is among the biggest open problems of fundamental physics. The
obstacles are of formal and of conceptual nature. Here, I address the main
conceptual problems, discuss their present status and outline further
directions of research. For this purpose, the main current approaches to
quantum gravity are briefly reviewed and compared.
| [
{
"created": "Wed, 15 Jan 2014 13:43:36 GMT",
"version": "v1"
}
] | 2014-01-16 | [
[
"Kiefer",
"Claus",
""
]
] | The search for a consistent and empirically established quantum theory of gravity is among the biggest open problems of fundamental physics. The obstacles are of formal and of conceptual nature. Here, I address the main conceptual problems, discuss their present status and outline further directions of research. For this purpose, the main current approaches to quantum gravity are briefly reviewed and compared. |
1307.2969 | Yu-Xiao Liu | Ke Yang, Xiao-Long Du, Yu-Xiao Liu | Linear perturbations in Eddington-inspired Born-Infeld gravity | 11 pages, no figures, published version | Phys. Rev. D 88, 124037 (2013) | 10.1103/PhysRevD.88.124037 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the full linear perturbations of a homogeneous and isotropic
spacetime in the Eddington-inspired Born-Infeld gravity. The stability of the
perturbations are analyzed in the Eddington regime. We find that, for positive
$\kappa$, the scalar modes are stable in the infinite wavelength limit ($k=0$)
but unstable for $k\neq0$. The vector modes are stable and the tensor mode is
unstable in the Eddington regime, independent of the wave vector $k$. However,
these modes are unstable and hence cause the instabilities for negative
$\kappa$.
| [
{
"created": "Thu, 11 Jul 2013 04:16:27 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Jul 2013 12:01:15 GMT",
"version": "v2"
},
{
"created": "Sun, 5 Jan 2014 08:29:29 GMT",
"version": "v3"
}
] | 2014-01-07 | [
[
"Yang",
"Ke",
""
],
[
"Du",
"Xiao-Long",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | We study the full linear perturbations of a homogeneous and isotropic spacetime in the Eddington-inspired Born-Infeld gravity. The stability of the perturbations are analyzed in the Eddington regime. We find that, for positive $\kappa$, the scalar modes are stable in the infinite wavelength limit ($k=0$) but unstable for $k\neq0$. The vector modes are stable and the tensor mode is unstable in the Eddington regime, independent of the wave vector $k$. However, these modes are unstable and hence cause the instabilities for negative $\kappa$. |
gr-qc/9910076 | Tetsuya Shiromizu | Tetsuya Shiromizu, Kei-ichi Maeda, Misao Sasaki | The Einstein Equations on the 3-Brane World | 8 pages, references added | Phys.Rev.D62:024012,2000 | 10.1103/PhysRevD.62.024012 | DAMTP-1999-150; NI99018-SFU; UTAP-349; RESCEU-40/99; WU-AP/85/99;
OUTAP-103 | gr-qc astro-ph hep-ph hep-th | null | We carefully investigate the gravitational equations of the brane world, in
which all the matter forces except gravity are confined on the 3-brane in a
5-dimensional spacetime with $Z_2$ symmetry.
We derive the effective gravitational equations on the brane, which reduce to
the conventional Einstein equations in the low energy limit. {}From our general
argument we conclude that the first Randall & Sundrum-type theory (RS1)
[hep-ph/9905221] predicts that the brane with the negative tension is an
anti-gravity world and hence should be excluded from the physical point of
view. Their second-type theory (RS2) [hep-th/9906064] where the brane has the
positive tension provides the correct signature of gravity. In this latter
case, if the bulk spacetime is exactly anti-de Sitter, generically the matter
on the brane is required to be spatially homogeneous because of the Bianchi
identities. By allowing deviations from anti-de Sitter in the bulk, the
situation will be relaxed and the Bianchi identities give just the relation
between the Weyl tensor and the energy momentum tensor. In the present brane
world scenario, the effective Einstein equations cease to be valid during an
era when the cosmological constant on the brane is not well-defined, such as in
the case of the matter dominated by the potential energy of the scalar field.
| [
{
"created": "Fri, 22 Oct 1999 09:33:09 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Oct 1999 11:06:29 GMT",
"version": "v2"
},
{
"created": "Mon, 17 Jan 2000 11:21:52 GMT",
"version": "v3"
}
] | 2009-10-09 | [
[
"Shiromizu",
"Tetsuya",
""
],
[
"Maeda",
"Kei-ichi",
""
],
[
"Sasaki",
"Misao",
""
]
] | We carefully investigate the gravitational equations of the brane world, in which all the matter forces except gravity are confined on the 3-brane in a 5-dimensional spacetime with $Z_2$ symmetry. We derive the effective gravitational equations on the brane, which reduce to the conventional Einstein equations in the low energy limit. {}From our general argument we conclude that the first Randall & Sundrum-type theory (RS1) [hep-ph/9905221] predicts that the brane with the negative tension is an anti-gravity world and hence should be excluded from the physical point of view. Their second-type theory (RS2) [hep-th/9906064] where the brane has the positive tension provides the correct signature of gravity. In this latter case, if the bulk spacetime is exactly anti-de Sitter, generically the matter on the brane is required to be spatially homogeneous because of the Bianchi identities. By allowing deviations from anti-de Sitter in the bulk, the situation will be relaxed and the Bianchi identities give just the relation between the Weyl tensor and the energy momentum tensor. In the present brane world scenario, the effective Einstein equations cease to be valid during an era when the cosmological constant on the brane is not well-defined, such as in the case of the matter dominated by the potential energy of the scalar field. |
2405.20349 | Vahideh Memari Rishakani | M. Halilsoy and V. Memari | Charged particle geodesics and closed timelike curves in an
electromagnetic universe | 13 pages, 5 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The spinning electromagnetic universe, known also as the Rotating
Bertotti-Robinson(RBR) spacetime is considered as a model to represent our
cosmos. The model derives from different physical considerations, such as
colliding waves, throat region, and near horizon geometry of the Kerr-Newman
black hole. Our interest is whether such a singularity-free spinning cosmology
gives rise to a natural direction of flow, a 'chirality' for charged particles.
Homochiral structures are known to be crucial for biology to start. Our concern
here is cosmology rather than biology, but as in biology, the stable structures
in cosmology may also rely on homochiral elements. We show the occurrence of
closed timelike curves a 'la' G{\"o}del. Such curves, however, seem possible
only at localized cell structures, not at large scales, but according to our
prescription of near horizon geometry, they arise in the vicinity of any
charged, spinning black hole.
| [
{
"created": "Mon, 27 May 2024 09:08:08 GMT",
"version": "v1"
}
] | 2024-06-03 | [
[
"Halilsoy",
"M.",
""
],
[
"Memari",
"V.",
""
]
] | The spinning electromagnetic universe, known also as the Rotating Bertotti-Robinson(RBR) spacetime is considered as a model to represent our cosmos. The model derives from different physical considerations, such as colliding waves, throat region, and near horizon geometry of the Kerr-Newman black hole. Our interest is whether such a singularity-free spinning cosmology gives rise to a natural direction of flow, a 'chirality' for charged particles. Homochiral structures are known to be crucial for biology to start. Our concern here is cosmology rather than biology, but as in biology, the stable structures in cosmology may also rely on homochiral elements. We show the occurrence of closed timelike curves a 'la' G{\"o}del. Such curves, however, seem possible only at localized cell structures, not at large scales, but according to our prescription of near horizon geometry, they arise in the vicinity of any charged, spinning black hole. |
0911.3889 | Carlos Palenzuela | Carlos Palenzuela, Luis Lehner, Shin Yoshida | Understanding possible electromagnetic counterparts to loud
gravitational wave events: Binary black hole effects on electromagnetic
fields | 12 pages | Phys.Rev.D81:084007,2010 | 10.1103/PhysRevD.81.084007 | pi-other-166 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In addition to producing loud gravitational waves (GW), the dynamics of a
binary black hole system could induce emission of electromagnetic (EM)
radiation by affecting the behavior of plasmas and electromagnetic fields in
their vicinity. We here study how the electromagnetic fields are affected by a
pair of orbiting black holes through the merger. In particular, we show how the
binary's dynamics induce a variability in possible electromagnetically induced
emissions as well as an enhancement of electromagnetic fields during the
late-merge and merger epochs. These time dependent features will likely leave
their imprint in processes generating detectable emissions and can be exploited
in the detection of electromagnetic counterparts of gravitational waves.
| [
{
"created": "Thu, 19 Nov 2009 20:48:18 GMT",
"version": "v1"
}
] | 2010-04-21 | [
[
"Palenzuela",
"Carlos",
""
],
[
"Lehner",
"Luis",
""
],
[
"Yoshida",
"Shin",
""
]
] | In addition to producing loud gravitational waves (GW), the dynamics of a binary black hole system could induce emission of electromagnetic (EM) radiation by affecting the behavior of plasmas and electromagnetic fields in their vicinity. We here study how the electromagnetic fields are affected by a pair of orbiting black holes through the merger. In particular, we show how the binary's dynamics induce a variability in possible electromagnetically induced emissions as well as an enhancement of electromagnetic fields during the late-merge and merger epochs. These time dependent features will likely leave their imprint in processes generating detectable emissions and can be exploited in the detection of electromagnetic counterparts of gravitational waves. |
1409.2607 | Hirofumi Sakuma | Hirofumi Sakuma | Note on a novel vortex dynamics of spacetime as a heuristic model of the
vacuum energy | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Vortex or spin is an important and ubiquitous form of motions existing in
almost all scale ranges of the universe and its dynamics is still an active
research theme in the classical as well as modern physics. As a novel attempt
of such studies, here we show that a class of vortex dynamics generated by
newly defined Clebsch parametrised (CP) flows parallel to geodesics exhibits an
intriguing property that it is isomorphic to the spacetime structure itself on
which it is defined in the sense that its energy-momentum conservation equation
automatically assumes exactly the same form as the Einstein field equation.
Implications of the existence of such a model is briefly discussed from the
view point of a current hot cosmological interest on dark energy together with
elusive concept on gravitational energy radiation.
| [
{
"created": "Tue, 9 Sep 2014 06:06:55 GMT",
"version": "v1"
}
] | 2014-09-10 | [
[
"Sakuma",
"Hirofumi",
""
]
] | Vortex or spin is an important and ubiquitous form of motions existing in almost all scale ranges of the universe and its dynamics is still an active research theme in the classical as well as modern physics. As a novel attempt of such studies, here we show that a class of vortex dynamics generated by newly defined Clebsch parametrised (CP) flows parallel to geodesics exhibits an intriguing property that it is isomorphic to the spacetime structure itself on which it is defined in the sense that its energy-momentum conservation equation automatically assumes exactly the same form as the Einstein field equation. Implications of the existence of such a model is briefly discussed from the view point of a current hot cosmological interest on dark energy together with elusive concept on gravitational energy radiation. |
1805.11626 | Steffen Gielen | Steffen Gielen, Rodrigo de Leon Ardon, Roberto Percacci | Gravity with more or less gauging | 24 pages, 1 table, 1 figure; minor changes to match published version | Class. Quantum Grav. 35 (2018), 195009 | 10.1088/1361-6382/aadbd1 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General Relativity is usually formulated as a theory with gauge invariance
under the diffeomorphism group, but there is a 'dilaton' formulation where it
is in addition invariant under Weyl transformations, and a 'unimodular'
formulation where it is only invariant under the smaller group of special
diffeomorphisms. Other formulations with the same number of gauge generators,
but a different gauge algebra, also exist. These different formulations provide
examples of what we call 'inessential gauge invariance', 'symmetry trading' and
'linking theories'; they are locally equivalent, but may differ when global
properties of the solutions are considered. We discuss these notions in the
Lagrangian and Hamiltonian formalism.
| [
{
"created": "Tue, 29 May 2018 18:00:12 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Aug 2018 15:21:59 GMT",
"version": "v2"
}
] | 2018-09-11 | [
[
"Gielen",
"Steffen",
""
],
[
"Ardon",
"Rodrigo de Leon",
""
],
[
"Percacci",
"Roberto",
""
]
] | General Relativity is usually formulated as a theory with gauge invariance under the diffeomorphism group, but there is a 'dilaton' formulation where it is in addition invariant under Weyl transformations, and a 'unimodular' formulation where it is only invariant under the smaller group of special diffeomorphisms. Other formulations with the same number of gauge generators, but a different gauge algebra, also exist. These different formulations provide examples of what we call 'inessential gauge invariance', 'symmetry trading' and 'linking theories'; they are locally equivalent, but may differ when global properties of the solutions are considered. We discuss these notions in the Lagrangian and Hamiltonian formalism. |
1211.1407 | Mu-Tao Wang | Mu-Tao Wang | Quasilocal mass and surface Hamiltonian in spacetime | 11 pages, contribution to ICMP 2012 | null | null | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the concepts of energy and mass in relativity. On a finitely
extended spatial region, they lead to the notion of quasilocal energy/mass for
the boundary 2-surface in spacetime. A new definition was found in [27] that
satisfies the positivity, rigidity, and asymptotics properties. The definition
makes use of the surface Hamiltonian term which arises from Hamilton-Jacobi
analysis of the gravitation action. The reference surface Hamiltonian is
associated with an isometric embedding of the 2-surface into the Minkowski
space. We discuss this new definition of mass as well as the reference sur-
face Hamiltonian. Most of the discussion is based on joint work with PoNing
Chen and Shing-Tung Yau.
| [
{
"created": "Tue, 6 Nov 2012 21:40:56 GMT",
"version": "v1"
}
] | 2012-11-08 | [
[
"Wang",
"Mu-Tao",
""
]
] | We discuss the concepts of energy and mass in relativity. On a finitely extended spatial region, they lead to the notion of quasilocal energy/mass for the boundary 2-surface in spacetime. A new definition was found in [27] that satisfies the positivity, rigidity, and asymptotics properties. The definition makes use of the surface Hamiltonian term which arises from Hamilton-Jacobi analysis of the gravitation action. The reference surface Hamiltonian is associated with an isometric embedding of the 2-surface into the Minkowski space. We discuss this new definition of mass as well as the reference sur- face Hamiltonian. Most of the discussion is based on joint work with PoNing Chen and Shing-Tung Yau. |
2004.05081 | Igor Fomin | A.N. Morozov, V.I. Pustovoit and I.V. Fomin | Bound gravitational waves in a dielectric medium and a constant magnetic
field | 8 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A description is made of the process of excitation of bound
longitudinal-transverse gravitational waves during the propagation of
electromagnetic waves in a dielectric medium. It is shown that the speed of
such gravitational waves is less than the speed of light in a vacuum and
coincides with the speed of an electromagnetic wave in matter. A description of
the propagation of a bound gravitational waves in a dielectric in the presence
of a constant magnetic field is suggested as well. It is claimed that these
gravitational waves in a dielectric medium are forced ones and they cannot
exist in a free state.
| [
{
"created": "Fri, 10 Apr 2020 15:53:27 GMT",
"version": "v1"
}
] | 2020-04-13 | [
[
"Morozov",
"A. N.",
""
],
[
"Pustovoit",
"V. I.",
""
],
[
"Fomin",
"I. V.",
""
]
] | A description is made of the process of excitation of bound longitudinal-transverse gravitational waves during the propagation of electromagnetic waves in a dielectric medium. It is shown that the speed of such gravitational waves is less than the speed of light in a vacuum and coincides with the speed of an electromagnetic wave in matter. A description of the propagation of a bound gravitational waves in a dielectric in the presence of a constant magnetic field is suggested as well. It is claimed that these gravitational waves in a dielectric medium are forced ones and they cannot exist in a free state. |
2211.02008 | Devansh Shukla | Devansh Shukla, Abhay Menon A, Kamlesh Pathak | Orbital Motion of a test particle around a Schwarzschild's Black Hole in
STVG gravity | 7 pages, 6 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this article, we have examined the existence of a static spherically
symmetric solution in the Scalar Tensor Vector Gravity (STVG) and investigated
its horizon distances to develop boundary limitations for our test particle. We
have computed the Kretschmann invariant of the metric to study the
singularities and verify that it reduces to general relativity's Kretschmann
invariant as $\alpha\rightarrow0$. Further, we investigated the orbital motion
of a time-like and light-like test particle around the static solution by
developing an effective potential and the radius of the innermost stable
circular orbit (ISCO).
| [
{
"created": "Thu, 3 Nov 2022 17:26:12 GMT",
"version": "v1"
}
] | 2022-11-04 | [
[
"Shukla",
"Devansh",
""
],
[
"A",
"Abhay Menon",
""
],
[
"Pathak",
"Kamlesh",
""
]
] | In this article, we have examined the existence of a static spherically symmetric solution in the Scalar Tensor Vector Gravity (STVG) and investigated its horizon distances to develop boundary limitations for our test particle. We have computed the Kretschmann invariant of the metric to study the singularities and verify that it reduces to general relativity's Kretschmann invariant as $\alpha\rightarrow0$. Further, we investigated the orbital motion of a time-like and light-like test particle around the static solution by developing an effective potential and the radius of the innermost stable circular orbit (ISCO). |
1403.0771 | Francisco Lobo | Tiberiu Harko, Francisco S. N. Lobo, M. K. Mak | Wormhole geometries supported by quark matter at ultra-high densities | 11 pages. V2: 12 pages, major revision and modifications; accepted
for publication in the International Journal of Modern Physics D | Int.J.Mod.Phys.D24:1550006,2015 | 10.1142/S0218271815500066 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A fundamental ingredient in wormhole physics is the presence of exotic
matter, which involves the violation of the null energy condition. In this
context, we investigate the possibility that wormholes could be supported by
quark matter at extreme densities. Theoretical and experimental investigations
of the structure of baryons show that strange quark matter, consisting of the
u, d and s quarks, is the most energetically favorable state of baryonic
matter. Moreover, at ultra-high densities, quark matter may exist in a variety
of superconducting states, namely, the Color-Flavor-Locked (CFL) phase.
Motivated by these theoretical models, we explore the conditions under which
wormhole geometries may be supported by the equations of state considered in
the theoretical investigations of quark-gluon interactions. For the description
of the normal quark matter we adopt the Massachusetts Institute of Technology
(MIT) bag model equation of state, while the color superconducting quark phases
are described by a first order approximation of the free energy. By assuming
specific forms for the bag and gap functions, several wormhole models are
obtained for both normal and superconducting quark matter. The effects of the
presence of an electrical charge are also taken into account.
| [
{
"created": "Tue, 4 Mar 2014 12:57:21 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Oct 2014 22:04:23 GMT",
"version": "v2"
}
] | 2014-11-13 | [
[
"Harko",
"Tiberiu",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Mak",
"M. K.",
""
]
] | A fundamental ingredient in wormhole physics is the presence of exotic matter, which involves the violation of the null energy condition. In this context, we investigate the possibility that wormholes could be supported by quark matter at extreme densities. Theoretical and experimental investigations of the structure of baryons show that strange quark matter, consisting of the u, d and s quarks, is the most energetically favorable state of baryonic matter. Moreover, at ultra-high densities, quark matter may exist in a variety of superconducting states, namely, the Color-Flavor-Locked (CFL) phase. Motivated by these theoretical models, we explore the conditions under which wormhole geometries may be supported by the equations of state considered in the theoretical investigations of quark-gluon interactions. For the description of the normal quark matter we adopt the Massachusetts Institute of Technology (MIT) bag model equation of state, while the color superconducting quark phases are described by a first order approximation of the free energy. By assuming specific forms for the bag and gap functions, several wormhole models are obtained for both normal and superconducting quark matter. The effects of the presence of an electrical charge are also taken into account. |
0807.3872 | Valerio Bozza | V. Bozza | A comparison of approximate gravitational lens equations and a proposal
for an improved new one | 11 pages, 6 figures, to appear on Physical Review D | Phys.Rev.D78:103005,2008 | 10.1103/PhysRevD.78.103005 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Keeping the exact general relativistic treatment of light bending as a
reference, we compare the accuracy of commonly used approximate lens equations.
We conclude that the best approximate lens equation is the Ohanian lens
equation, for which we present a new expression in terms of distances between
observer, lens and source planes. We also examine a realistic gravitational
lensing case, showing that the precision of the Ohanian lens equation might be
required for a reliable treatment of gravitational lensing and a correct
extraction of the full information about gravitational physics.
| [
{
"created": "Thu, 24 Jul 2008 12:44:08 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Oct 2008 21:26:53 GMT",
"version": "v2"
}
] | 2008-12-18 | [
[
"Bozza",
"V.",
""
]
] | Keeping the exact general relativistic treatment of light bending as a reference, we compare the accuracy of commonly used approximate lens equations. We conclude that the best approximate lens equation is the Ohanian lens equation, for which we present a new expression in terms of distances between observer, lens and source planes. We also examine a realistic gravitational lensing case, showing that the precision of the Ohanian lens equation might be required for a reliable treatment of gravitational lensing and a correct extraction of the full information about gravitational physics. |
2202.12681 | Charles Robson | Charles W. Robson and Marco Ornigotti | Take the A-Metric: Interpretations of Some Known Solutions of Einstein's
Vacuum Field Equations | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we present a new interpretation of the only static vacuum
solution of Einstein's field equations with planar symmetry, the Taub solution.
This solution is a member of the $AIII$ class of metrics, along with the type D
Kasner solution. Various interpretations of these solutions have been put
forward previously in the literature, however, some of these interpretations
have suspect features and are not generally considered physical. Using a simple
mathematical analysis, we show that a novel interpretation of the Taub solution
is possible and that it naturally emerges from the radial, near-singularity
limit of negative-mass Schwarzschild spacetime. A new, more transparent
derivation is also given showing that the type D Kasner metric can be
interpreted as a region of spacetime deep within a positive-mass Schwarzschild
black hole. The dual nature of this class of $A$-metrics is thereby
demonstrated.
| [
{
"created": "Fri, 25 Feb 2022 13:36:29 GMT",
"version": "v1"
}
] | 2022-02-28 | [
[
"Robson",
"Charles W.",
""
],
[
"Ornigotti",
"Marco",
""
]
] | In this work, we present a new interpretation of the only static vacuum solution of Einstein's field equations with planar symmetry, the Taub solution. This solution is a member of the $AIII$ class of metrics, along with the type D Kasner solution. Various interpretations of these solutions have been put forward previously in the literature, however, some of these interpretations have suspect features and are not generally considered physical. Using a simple mathematical analysis, we show that a novel interpretation of the Taub solution is possible and that it naturally emerges from the radial, near-singularity limit of negative-mass Schwarzschild spacetime. A new, more transparent derivation is also given showing that the type D Kasner metric can be interpreted as a region of spacetime deep within a positive-mass Schwarzschild black hole. The dual nature of this class of $A$-metrics is thereby demonstrated. |
1005.5151 | Federico Piazza | Federico Piazza | Gauss-Codazzi thermodynamics on the timelike screen | 8+1 pages, final version | Phys.Rev.D82:084004,2010 | 10.1103/PhysRevD.82.084004 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is a known result by Jacobson that the flux of energy-matter through a
local Rindler horizon is related with the expansion of the null generators in a
way that mirrors the first law of thermodynamics. We extend such a result to a
timelike screen of observers with finite acceleration. Since timelike curves
have more freedom than null geodesics, the construction is more involved than
Jacobson's and few geometrical constraints need to be imposed: the observers'
acceleration has to be constant in time and everywhere orthogonal to the
screen. Moreover, at any given time, the extrinsic curvature of the screen has
to be flat. The latter requirement can be weakened by asking that the extrinsic
curvature, if present at the beginning, evolves in time like on a cone and just
rescales proportionally to the expansion.
| [
{
"created": "Thu, 27 May 2010 19:14:12 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Oct 2010 15:43:43 GMT",
"version": "v2"
}
] | 2014-11-21 | [
[
"Piazza",
"Federico",
""
]
] | It is a known result by Jacobson that the flux of energy-matter through a local Rindler horizon is related with the expansion of the null generators in a way that mirrors the first law of thermodynamics. We extend such a result to a timelike screen of observers with finite acceleration. Since timelike curves have more freedom than null geodesics, the construction is more involved than Jacobson's and few geometrical constraints need to be imposed: the observers' acceleration has to be constant in time and everywhere orthogonal to the screen. Moreover, at any given time, the extrinsic curvature of the screen has to be flat. The latter requirement can be weakened by asking that the extrinsic curvature, if present at the beginning, evolves in time like on a cone and just rescales proportionally to the expansion. |
0805.3318 | Bernd Schroers | Catherine Meusburger and Bernd Schroers | Generalised Chern-Simons actions for 3d gravity and kappa-Poincare
symmetry | 31 pages, minor corrections and additional comments | Nucl.Phys.B806:462-488,2009 | 10.1016/j.nuclphysb.2008.06.023 | EMPG-08-05, pi-qg-79 | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider Chern-Simons theories for the Poincare, de Sitter and anti-de
Sitter groups in three dimensions which generalise the Chern-Simons formulation
of 3d gravity. We determine conditions under which kappa-Poincare symmetry and
its de Sitter and anti-de Sitter analogues can be associated to these theories
as quantised symmetries. Assuming the usual form of those symmetries, with a
timelike vector as deformation parameter, we find that such an association is
possible only in the de Sitter case, and that the associated Chern-Simons
action is not the gravitational one. Although the resulting theory and 3d
gravity have the same equations of motion for the gauge field, they are not
equivalent, even classically, since they differ in their symplectic structure
and the coupling to matter. We deduce that kappa-Poincare symmetry is not
associated to either classical or quantum gravity in three dimensions. Starting
from the (non-gravitational) Chern-Simons action we explain how to construct a
multi-particle model which is invariant under the classical analogue of
kappa-de Sitter symmetry, and carry out the first steps in that construction.
| [
{
"created": "Wed, 21 May 2008 17:35:03 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Jul 2008 15:15:10 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Meusburger",
"Catherine",
""
],
[
"Schroers",
"Bernd",
""
]
] | We consider Chern-Simons theories for the Poincare, de Sitter and anti-de Sitter groups in three dimensions which generalise the Chern-Simons formulation of 3d gravity. We determine conditions under which kappa-Poincare symmetry and its de Sitter and anti-de Sitter analogues can be associated to these theories as quantised symmetries. Assuming the usual form of those symmetries, with a timelike vector as deformation parameter, we find that such an association is possible only in the de Sitter case, and that the associated Chern-Simons action is not the gravitational one. Although the resulting theory and 3d gravity have the same equations of motion for the gauge field, they are not equivalent, even classically, since they differ in their symplectic structure and the coupling to matter. We deduce that kappa-Poincare symmetry is not associated to either classical or quantum gravity in three dimensions. Starting from the (non-gravitational) Chern-Simons action we explain how to construct a multi-particle model which is invariant under the classical analogue of kappa-de Sitter symmetry, and carry out the first steps in that construction. |
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